I seriously beg to differ on that one. I suspect that a lot of the venomous and negative comments I keep seeing about FB are from people who don't use it and don't understand it.
I'll happily admit to using it. It is a great way to keep in touch, especially with my real-world friends who I don't get around to seeing that often but who I actively want to chat to and share pics and stuff with. I don't generally disclose my personal information to anyone but my friends, all of whom I know in the real world.
It is a big deal and social networking is absolutely here to stay. It's quite a new technology and a lot of it relies on innovation and cross referencing from different activities and sources. Therefore it's not surprising that there will be a few issues around privacy which will probably be ironed out in the course of time.
Hopefully it will become more sophisticated in the future and you will be able to separate out your work and leisure interests in FB without too many problems. FB already allows this to some extent with the Limited Profile option.