facebook has caught a lot of flak recently over privacy concerns. To be sure, facebook's default privacy settings are much more public than you would have expected fifteen years ago.
First, some background. Most people joined Thefacebook as an easy way to stay in contact with family and friends. People upload photos, talk about themselves, message their friends, and just communicate more than they used to. If you don't want to communicate any more than you did ten years ago, you probably didn't create an account. Since my generation joined (20, more or less), facebook has changed: likely your boss and grandmother are online, advertisements are targeted to your interests, and most recently, certain information from your profile is sent to other websites when you visit them.
This last part is causing the recent consternation. Savvy users can adjust their settings to make less things public, but certain information such as your name, friends, and your interests are public and stay that way. I recently read a study in which it was found that people can find out a lot of information about you by only looking at your public friends list.
However, the answer to the question, "What problems does this raise?" is difficult to find. I've noticed that all these arguments against facebook rely on a common axiom: Privacy is important. Is this really the case? If you're in hiding from the mafia or the FBI, I can definitely understand your concern. How exactly are the rest of us harmed by Pandora letting your friends know what kind of music you like? Is it so bad to learn that someone you know just purchased a similar book at Barnes & Noble, or also read an article at CNN? We all seem to have the idea that if we put a piece of information online, someone will find it and do x with it. I've applied all the math I can, and the only value of x that I can find is: have a more accurate idea of who you are.
An example often used to prove privacy's importance is that employers look at the facebook profiles of people they are interviewing. Your potential boss will find out that you like to watch Family Guy, listen to Lady Gaga, play football, and read Science Fiction. Perhaps he will notice from a picture that you sometimes enjoy an adult beverage. If you aren't hired on these justifications, I don't think you would have enjoyed the job anyway. Why should you temper your life to better fit someone else's expectations?
I am introverted and not, in general, a very social person. On the other hand, my profile is completely public information. Anyone with a facebook account can read this note and any part of my profile. If someone takes the time to look at my account they will find the best possible representation of me, perhaps even better than actually meeting me.
The accessibility of information has been increasing ever since the invention of the printing press. I'm confident that in a few short years, any information at all will be available to anyone in the world. Think of these implications! One only has to look at Google, Wikipedia, or yes, facebook to find how access to information is a good thing. At least the Luddites were angry that they were losing their jobs. Why are you rallying against the expansion of information?
In fairness, here's my facebook account