Looking for an old thread. Sometime between (I think) one and three years ago there was a very sophisticated “Internet scavenger hunt” thing started here. Not your typical “find these answers at Google” scavenger hunt, but one that required puzzle-solving and deductive reasoning as well.
The OP which started it (duh), if I remember correctly, part of the puzzle had to be deduced by realizing you needed information from the poster’s user profile. The question was something like “I can see this looking from my bedroom window”.
The answer was not just “this item” or “this building” but the URL that hosted this particular image or item or whatever.
At least, I think it was like that.