I do not want to force people to do x and y. The way I see it, whenever I see a really good photo I google search it or use tineye. If there is a hit I will look at the profile if I cannot find anything, like an introduction post or consistency in the posts this person makes I add them to the blacklist.
So the only requirement I would have is to have some kind of verification so I do not falsely flag said person
lol - you will never have to look up my photos! No one would claim them except me. I love taking them and I'm so glad to have a place to post even though I hang my head in shame often when I see your winners.
It is amazing how much you have to go through to keep these contests clean and I appreciate your efforts very much. You are right that a bot would probably give you more work as the photos are on other sites. Some of mine are on FAA/Pixels or Behance, so a bot would probably say I stole them from myself.
It's also a valid way :)
Cheers
I do the same thing and have had to disqualify a couple of people already in my contest, and I have not long started it!