When you meet someone online, (tinder, plenty of fish, ok Cupid, etc.) and you want to make sure they're not a total psycho before you meet them. So you look them up on Facebook to see what they post, who they're friends with, what pictures you haven't seen, etc. Sometimes you are surprised by what you find...
I was kind of skeptical about Todd, so I ran a Facebook background check to see who he really is...