Salim Virani on why you must get off Facebook:

According to the FTC settlement from a few years ago, after Facebook was sued by the US goverment for its privacy practices, Facebook is “required to prevent anyone from accessing a user’s material more than 30 days after the user has deleted his or her account;”

There are different interpretations of this. Some say you need to delete each post separately, others say delete your account, and some say they’ll still keep your data anyway — that all you can do is stop giving them more data.

I’m going to do both as a precaution. There are a few helpful browser add-ons that will delete your posts individually, which I’m running now but needs some baby-sitting to keep running. And some great instructions on actually deleting your account while Facebook tries to trick you into deactivating it instead.

He does a far better job verbalizing why this is important than I can, but the above quote is very telling if you ask me. Facebook makes it so hard to clean your data off their servers that people make tools to help you.