Hah...I knew what this was all about even before I opened the thread.
I think rabbit poop isn't that harmful as long as he doesn't eat "too much". How much is too much? I have no idea. I don't let mine eat it at all. Besides, people have been known to poison rabbits...I'm thinking some of that would wind up in the poop.
Teach "leave it" and use that to keep him away from piles...and hope he'll remember that even if you're not around. Good luck. Dan is usually good about that but once in a while slips.