Even after the IPO, Facebook may be hiding some things from users, according to SmartMoney.

They were in the right place at the right time

Industry observers say Facebook's success comes from luck, ambition and strategy.

In the beginning, Facebook was only available to college student at certain universities. That let Facebook decide where to market the site and protect it from growing too quickly, David Kirkpatrick, author of The Facebook Effect, told SmartMoney.

They know where you go online

Facebook has evolved a lot since it's creation. If Facebook users are logged in while they're browsing the web, Facebook can see where users go online, Nicole Ozer, a policy director at the ACLU of Northern California, told SmartMoney.

Facebook can track you offline too
Richard Drew, AP

Facebook launched Places in August, 2011, a service that let's people say where they were using the GPS on a smartphone.

Using the Places feature lets your friends check you into locations unless you disable the setting. That means other people can know what you're doing and where you're doing it.

Your account isn't really secure

Facebook is currently the second biggest brand on the internet, according to the monitoring service, PhishTank.

More and more scammers are stealing passwords and other personal data by acting as trusted sources. This is commonly referred to as phishing.

If it feels addictive, that's probably because it is

Some Facebook users form an online identity they struggle to live up to in the real world, Sherry Turkle, MIT professor of the social studies of science and technology, told SmartMoney. Others struggle because they get burned out because looking at others' pages is so easy.

If you're work or school performance suffers due to Facebook, you should get help, Michael Fraser, a clinical psychologist in New York, told SmartMoney.

Facebook gives brands, fans and headaches

Companies can make a Facebook page that users can become "fans" of and hear about deals and promotions. Companies can make money on that, but they can also have problems.

This makes it easy for customers to group together and complain. When Gap released a new logo in October 2010, the company's Facebook wall was covered with negative discussion.

Family and employers can see your info

Facebook changes the way people act. Parents and grandparents can follow their loved ones' lives, which can result in some awkward moments.

Employers can check potential employees' Facebook profiles to look at their personal life and background.

Apps can be hard to regulate

In mid-2007, Facebook launched a platform that let software developers put apps that run on the site. Now, there are hundreds of thousands of apps on the site.

Recently, some app developers were caught selling user information to a data collection firm.

Facebook says it's trying to crack down on such violators.

There are other social networking sites
Paul Sakuma, AP

Google+, LinkedIn, Twitter and location-sharer Foursquare, are all social networking sites in the U.S. And there are other sites outside of the country that may cause problems for Facebook.

Facebook still can't get into China and even if it did get into China, it would have to compete with other social networking sites.

It's free now, but it might not always be

Facebook has been looking for ways to increase revenue through non-advertising, the Wall Street Journal reported on Thursday.

That might result in users getting charged if they want their posts to be seen by all of their friends, putting ads on mobile devices and selling apps.

Facebook might adapt a model where the basic service is free but more advanced services will have fees.