Nice to see the comments, thanks!
Austin, your vision is possible but at least partially avoidable. It requires that the contest rules and names are written clearly. Category names like "Real reflections" and "Natural symmetry" could be used to guide the contest photos to be real photographs.
With real or non-manipulated photographs I do not mean that the contest photos should be unprocessed, colourless or unsharp. If I have understood the nature of digital photography right some kind of processing is needed every time if you want to get the best out of the frame you have captured in the camera. With the artificial elements I meant only the copied and pasted things that were not in the place when someone took the contest photograph.
Lady GooGoo La La, maybe the most effective way to search for the fake reflections and artificial symmetry is to start from the all too perfect or unbelievable looking photographs :). And when you do not find anything suspicious the photo feels even better. That's real fun and I vote for that!
Herman, I think that the contest is one of those things in Panoramio, where the team could easily stop to worry about the workload. By stopping the whole contest? Sorry, no :) I mean that the final checking about the 30 winner photos could be moved to some group of volunteers.
Personally I'm not irritated if people send their driver's license photos to the contest. It feels just ridiculous. I just would not be surprised if someday a happy owner of the new license with lots of pals will be the winner of the "Reflections". Without any reflection.