Your Facebook profile can be as private or as public as you want it to be, you have full control over what goes on. If someone tags you in a photo (which you don't like because it's not a very good photo of you... if stuff like this bothers you, you are gay), then you can quite easily remove the tag. You can also block that person from ever tagging you again if you wish.
Facebook is a very useful tool for keeping in touch with people and organising events with large groups of friends. I use it to organise a yearly gathering of my old school friends that otherwise would be a case of lots of "tell this person about this" and "ask that person about that" etc...
Also, it's very good for procrastination. At work I am able to complete my computer modelling and drawing work MUCH faster than the others can complete their sections, so I end up with a fair amount of dull spare time. Bejeweled Blitz is very good at filling this time
and if anyone else who plays it would like to add me on facebook, that would be sweet, because I have no competition on it. Because I get to play it a lot at work, I have now become legendary at it and no one on my facebook can even score half of my top score [V]