I've just read a story on Slashdot (well, its "unofficial digest", AlterSlash, to be more exact) about NSA and their funding of the research into harvesting of the information on social networking websites, written like it's some great, revolutionary discovery.
Just think about it a bit. Everyone has access to the information you publish on a social networking website – it's the whole point of a social networking web site. Why shouldn't the NSA have it, too – it's their job, after all? They'll just add the information they collect on those websites right next to your phone calls, bank transfers, health charts, grocery bills and many other things they already have about you. What's the big deal? You choose to publish the information freely on the 'net, it's your fault if they use it against you.
I'm not really using it actively because I rarely send any confidential information over the Internet, so I'm probably the last person who should be giving this kind of advice, but if you publish / send any sensitive information on the Internet and you don't want it to be publically available – use GPG or some other cryptography methods. It's not that hard – there is a great chance that there's a plug-in for your favorite e-mail client available – and it's secure.
I'm all for privacy and I believe that every person should have its own share of it, but if you publish something on a public website, make sure it's something you won't mind the whole world to read. It's public, after all. I am more worried about them collecting information which should be private.