Has anyone ever added someone on Facebook or MSN that you've never known?

A lot of people add me who I don't know. I usually accept their friend request. Then I check out their profile to see if they are some foreign creep or if I actually know them from somewhere. If they turn out to be some creep with no pictures or any information I delete them. I have added people who I didn't know before.. Maybe one time, I had to add a girl who was starting arguments with a friend to tell her off.

yes only if we have many mutual friends. and they have requested it.