I dont see why people feel the need to post every little detail about themselves on the internet. Even after i finished a big assignment on social networking for my course a few months back, i just couldnt see the pros anywhere near outweighing the cons.
Then again, i am a bit paranoid, so mabye people just dont see the same cons as i do, but i think its just stupid to post so much information about yourself on the internet. The only real pro in most social networking sites is finding people with the same interests as yourself, but the problem with that is, you can simply find people with the same interests by simply doing it. If your in to football, go play football and meet new people, If your into competative gaming, go to a LAN party. All of which are better ways IMO then to meet peopl online.