If it were to happen, it won't be for awhile yet. Maybe it could be suggested (if not already) that a separate section could be made for the contest(s).
I don't see the difference between posting photos of your bird(s) and a competition which again, it would be posting photos of your bird, only it's for a competition - no big deal really.
Why try ruin the fun people would like to have? it's your opinion, but if it's been successful on other forums without problems then it'd go pretty smoothly here. Again, that's why I said suggest perhaps a different section for it, if you don't like it you don't have to read that particular section where the contest is being done - stick to posting elsewhere if that's what you prefer.
It's not going to 'miss the point' of the forums because there's still going to be people posting that don't participate, not everyone is going to want to do it, but for those who do, it's not going to make you lose sleep over it.
As for being harassed I don't see any member forcing people to post photos, they from what I've seen, post at their own free will.