Friendster: Their cancel request resulted in an infinite reload of the proceeding page. I did confirm, however, that the account has been deleted.
MySpace: Who would ever leave MySpace? Well, I tried and I believe I was successful. They ask you two times before they send you a confirmation email that leads you to another 2 times: "Are you SURE?!?!?!" Seriously. They stated that it takes 48 hours to complete but at least it will be an account deletion, unlike...
Facebook: They won't let you leave. You can only "deactivate" your account which is "reactivated" the second you try to log back in. This smells like scandal or a pretty piece of software with some nasty bugs once you try to delete records.
I'm still on Last.fm.
Well, there you have it. AIM, MSN are next.
Why am I doing this? Well, if you really care you'll send me an email and ask. My email is my first name at this domain.