Random friend requests on Facebook from girls I don't know?

[Joe]

Every now and then I'll get a friend request from a girl I don't even know. So far I have gotten 3 of them. Even when I try looking at their profile to see if there is something about them that looks familiar, it appears that their accounts are fake. All I see are a few pictures and no personal information other than their name. Their friends list only lists like 10 or 15 people that were added recently.

So my question is, what is up with all of this? Is it a scam? I never bothered to accept any of them because I don't accept people I don't know over Facebook. Has anyone ever had this incident before?

I messaged one of them about a month ago and I never got a reply back.