Because, as you just demonstrated with your programming example: For HIM it's a glorified message board. Other people may use it in completely different ways and appreciate it for them.
I'm not the greatest facebook-fan either, but I think you're really overstating the control they have over people's lives here and at the same time understating the value it can provide to people. Unless of course all people using facebook are just damn idiots and don't know what they're getting themselves into!
EDIT: 'control over people's lives' might be better phrased as 'knowledge about their activities/preferences'