Facebook help: How can I be friends with someone I have never seen or met?

[musicislife]

Sometimes I go down my friends list and find someone who I have NO mutual friends with and I am almost 100% sure I have never met him or her.
How can this happen?

And yes my account is set to friends only for viewing!!!
I am not trying to add friends I just want to know how these people that I have never met or talked to end up on my friends list. I know people can change their profile pics and name but I try not to add unless I know 100% who he or she is!

[Gummy Roach]

The same way you do here on Yahoo Answers. Send them some e-mails, compliment them about something they wrote.

"Hey, I saw where you wrote ________, that's some funny stuff" or "I see you like __________ too."

And then see where it goes from there. If they don't respond, no worries, go on to the next person.
Don't over think this.