Thank You. Thank You. Thank You.
You sir have so far proven to be the MOST reasonable person commenting on this article.
I'm a geek, I also wanted to sit at home and code or whatever growing up. Social networking on the internet is a dream come true for me, and most likely for my offspring. There's absolutely nothing wrong with letting your kids use the internet, as long as (like you say) you arm them with a bit of knowledge first. Most of the people here who are posting against Social Networking probably have absolutely no idea what their kids are doing, or have caught their kids doing something naughty, or their kids have been victimized but some sort of incident. If you just trust your kids, and give them a bit of smarts (and respect), they'll trust you back and respect you back.
Once again, thank you for being the voice of reason. :)