I don't talk about it to anyone at my gym, but I know for a fact a ton of guys there are 'on'. When you start doing the shit it becomes obvious to you who else does them, and vice versa. But I don't trust people enough to start bringing up that shit and I'll give you a perfect example why.
A girl I know was selling a lot of ecstasy around town and ended up getting pinched with something like a hundred rolls (this was before the horror stories about ecstacy and all the media publicity started coming out and the subsequent crackdown). The guy who narced her out was a friend of hers for five or six years. He didn't do it b/c he was a cop or b/c he got caught and turned over on her. The fucking prick did it because he was a criminal justice major who wanted to get into the F.B.I. or D.E.A. after he graduated and thought narcing her out would go on some kind or record and help his chances of getting into one of these outfits.
My advice would be just keep your mouth shut and smile knowingly. You don't know what kind of crazy agendas people have or what they might do. 9 out of 10 people would turn in their best friend to stay out of trouble. Some of these punk bitches may also weigh 240 lbs.