For those of you on Facebook, beware of its ever changing privacy settings. Unfortunately there are multiple privacy settings and you have to have a master's degree in technology to figure out how to deal with it! Facebook is constantly changing its privacy related settings in response to--what else--money. Many of these settings are ones that you have to opt out of rather than choose to participate in.
Mashable has a nice explanation of the purposely confusing Facebook privacy issues and gives you steps to take for maximum privacy. For the newest in Facebook's manipulation and how to get around it ("Instant Personalization" which you have to opt out of) visit the Librarian By Day. Another good article is 10 Privacy Settings Every Facebook User Should Know.
One thing to remember is this: one of the easiest ways to ensure privacy on Facebook is not to use many of their applications, including "pages" and "likes" in the first place. I mean, does everyone who visits your page need to know where you work or even where you live? If so, fine. If not, don't put it. Or, as Mashable mentions, divide your friend list into categories and only share some things with some people.
Facebook privacy is a real issue and, unfortunately, it changes constantly.