I stopped promoting private tournaments awhile ago.. but when I was there was actually more than a bit of password passing that went on…
There were websites dedicated to sharing passwords, your tournament would be posted on the site, with the theifs banner, and your password. There was also a newsletter or two that went out with stolen passwords in it, I actually used to get it, I don’t still, so I likely blocked it eventually, I’m sure I just searched google to come up with them, maybe try private tournament or something like that and see wht you find.
I did at first report quite a few of the people, websites etc. to a few of the poker rooms, none seemed overly concerned.
I finally began requiring 4 posts on the forum during the month of the game, then PMed the password to only those forum members, we had a good tournout, but frankly, the tournaments mostly draw freeroll chasers, so I eventually stopped bothering much.
Good Luck