It can depend a bit on geography. Facebook.jp has a suspiciously high number of attractive young ladies in Ogaki (as in, literally, more than the number of 18 to 22 year old young ladies in Ogaki) who send friend requests for, I assume, the purpose of developing marks for scams.

I'm also one degree of separation from two countries in Southeast Asia and this causes me to get a lot of friend requests of dubious provenance.