It's four part series overseeing the successes and controversies of Facebook.

Last Wednesday through Friday, we examined the background and leadership of the company's founder, the software development that brought anger and popularity to the social network and an international controversy that jolted public trust in Facebook.

You can find all of these shows in our archives section at CNN, Tenn dot com and meantime CNN dot com has coverage of breaking news from around the world will be resuming our Daily news reporting tomorrow.

But as we bring you Installment four of four on Facebook today, Lori Siegel looks at how the company manages some of the problems that come up issues that could go viral controversies both on the platform and among the people who run it through the words of both current and former Facebook employees.

Did making money get in the way of Facebook's mission toe ultimately connect the world?

I don't think so.

The fundamental business model we offer, I think, is a really good one.

It protects people's privacy, and it takes a very powerful product that changes people's lives and makes it available for free.

So if we were to have to charge for Facebook, we did have an ad business.

A very small fraction of the people who use it would be able to use it.

They would say, How else are we gonna connect the whole world if it's not free?

But I would say if the thing you're connecting the whole world to isn't safe, it shouldn't be free.

Unsafe critics like Tristan Harris say not just because of personal data breaches, but also unsafe because of the content that seems unchecked on the platform, something Congress was worried about on Day two of Zuckerberg's testimony.

Do we?

I have a responsibility for the content that people share on Facebook, and I believe the answer to that question is yes.

Facebook is now investing millions in policing content, adding thousands of content reviewers to the payroll and developing artificial intelligence they hope will help identify troublesome material.

But the answers aren't always clear judging hate speech imagery.

I saw it in this room, Ah, bi weekly meeting of Facebook employees devoted to content policies.

They often discuss what post stay up and which ones are taken down.

In this case, it was striking The hear conversations we'd have in a newsroom happen at a tech company and if unanswered here, content decisions go all the way up to the top of the Facebook food chain to Mark and Cheryl.

This is like an editor in chief role.

I mean, should you be making that decision?

Well, I think as little as possible, which is why I focused on designing the systems because there are going to be billions of pieces of content that people post every day.

And I think getting it right at a systems level is more important.

But with billions of content hits daily, problems at this scale go viral, and decisions made behind the scenes are increasingly scrutinized.

I've heard you guys talk a lot about transparency it, but then you have these reports coming out that say something otherwise.

So how?

And I guess I ask it again.

How do you ensure that you do win back public trust?

Yeah, I don't think that the right expectation is that there aren't going to be issues.

I think the question is, how do we address them, a question the company is struggling with.

While executives have promised to focus on security and transparency.

We have more than doubled the number of people we have working in safety and security, according to the report.

They not only ignored warning signs but sought to conceal them.

So set the record straight.

I mean, it's a Facebook attempted to downplay the significance of Russian activity in the run up to the 2016 election today.

I mean, after we found these things, I'm not totally happy with what the communication strategy was.

Former chief security officer Alex Tamils found himself in the news again.

Everything.

And so we went back to interview him.

I think we could have been much more aggressive about talking about what we knew right after the election, probably even before the election.

Obviously, there are all kinds of internal miscommunications, one of the problems about having a really tight knit set of people making all these decisions.

If you keep the same people in the same places, it's just very difficult to admit you're wrong, right?

The company is powerful, and after spending time behind Facebook's walls, there was another theme that emerged.

Folks who had something to say but were afraid to say it Ironically, in a place that's connected billions, this former employee cites a disconnect with Facebook is in transition.

Many executives have leftover rumor disputes about the company's direction, including the founders of INSTAGRAM and what's up.

Amidst all the controversy, there's been speculation.

Should Zuckerberg, who is CEO chairman and the majority shareholder in Facebook?

Step aside, that's not that's not the plan.

Would anything change that?

I mean, like, eventually, over time, I'm not gonna not gonna be doing this forever.

Many of the employees you've met in the show have left hopefully will give you a kind of a pretty good understanding, including Alex Stamos, who is now teaching future entrepreneurs at Stanford University.

Doing better means doing things like this, bringing people together to think about these problems early and and not just be reactive, You know, having a real diverse set of people work on these work in tech and work in Silicon Valley is gonna be critical for that.

Randi Zuckerberg is building a media company that focuses on getting more young women in the tech world.

You've always viewed your brother's a creator.

How do you feel as his sister about people genuinely questioning the impact of his creation and whether it's good for humanity.

He has always just been an incredible trail blazer of pushing the boundaries.

You know what he sees, where he sees the world should go.

And, you know, he has pushed a lot of us to think of the world in a bigger, more connected way than we ever thought it would be.

So no, for better or worse, Mark is not the kind of person who is swayed by what you or I or anyone thinks of him.

And, uh, because of that, I think we're gonna get a lot more amazing things out of him in the years to come.

At 34 Zuckerberg is one of the most powerful people in the world.

He's pledged his fortune to charity, and there is no denying people have used Facebook to raise over a $1,000,000,000 in charitable causes throughout the years.

By every metric, Facebook is a success.

It's revenue in 2018 $55.8 billion.

It was just 272 million in 2008.

But Facebook, at 15 faces complicated questions.

A ripple effect of Zuckerberg's mission is what's good for business, good for society.

And what is the cost of connecting the world?

Right now, the tech industry has been telling themselves narrative that connect people of platform for free speech.

It's just automatically good.

I think the deeper upgrade we have to make is a philosophical upgrade, which is what does it mean for these things to be good?

Facebook is a living, breathing map of society, and it's literally a map of every single person in all of the relationships and all of the interactions between all those relationships.

And so, in a way, it's is messy and human as we all are.

It is hard to say what any individual can do in the face of these massive, kind of historical forces that that were at the intersection of right.

What happens when you give voice to billions of people for the first time in history?

Do you think he'll be on the right side of history when we look back on this period?

Yeah, I do.

I think it's hard to imagine a future we're giving people more power and helping people connect and share more ideas isn't going to end up being a very positive thing, although we're at a moment where a lot of people are watching Facebook and wondering can do all those things the principles of how do you balance giving people a voice with keeping people safe?

How do you make sure that you can protect people's privacy and use information away?

The people are comfortable with, while at the same time being able to build a system that can go stop bad guys from doing things and can provide a service, that it's free for people around the world.

These air really big historical questions, and they're not simple things that have one sentence answers.

And over time, I really believe that being on the side of giving people power and giving individuals of voice and giving people the ability to connect to the people that they want to is going to be the thing that wins out.

With a digital world of more than two billion people, Facebook has become part of the fabric of society, revealing both the best and the worst of humanity.

For a tech company that has extraordinary human impact.

What the next 15 years looks like is unknown.

We do know one thing as we head into uncharted territory, Zuckerberg's mission to connect the world will only amplify as well the issues that come along with it.