Facebook was a wonderful way for me to keep in touch with a lot of different people, but I deleted my account a few weeks ago.
I know that my leaving Facebook has absolutely no effect on the site and isn’t going to influence their policies. That’s not why I left: I left Facebook because it offended my ethics and endangered me professionally.
If you’re worried about privacy on facebook, but don’t want to delete your account, try this tool to help you fix some of the privacy issues. Otherwise, delete your account and check out the Diaspora project.