My 2 cents:

Use e-mail if you want to help someone out, but want to be stealthy about it. Don't respond at all if you don't want to attract attention to the crick in question.

Some folks have been known to respond with a bit of misdirection, as in, "Been fishing there for two weeks, haven't caught squat, nor have any of my buddies."

If the stream has a boat ramp on it, you'll have a lot of work to do to get me to think it's a zipper. I still may choose not to speak about it, but I don't hink it's fair to climb somone's backside if they do mention it. This is, after all, a forum for the sharing of information.