I wouldn't sweat it....
Check out this post by ShoeMoney about this very thing.
I mean don't advertise instructions on how to copy your idea but don't sweat it if someone does.
I own a very large forum and a small forum in great niches that earn me a ridiculous amount per click via adsense. I never ever mention them in any forums I visit and very few people that I know even know I have anything to do with them.
Since you wont likely need a webmaster forum to promote your idea there is no need to ever mention specific details here.
So the longer it takes for a webmaster to figure it out the better off you'll be.