where do selfies on the internet come from?

assume we take a random sexy guy tumblr or /r/gaybrosgonewild, how many of those photos were posted by the person in the photo?i can't imagine anyone having any accurate and statistically significant data, so maybe let's say, have you ever come across a photo that you are certain wasn't originally posted on the internet by the subject of the photo (excluding famous people)?or conversely, have you ever been the first person to put something private someone sent you onto the internet? i'm thinking specifically of those pics that clearly look like they were snagged from kik or snapchat or something...bonus questions: how many sexy internet photo subject people do you actually know in real life? I don't think i've ever met anyone in real life then seen them naked on the internet (met as in conversed with)...