I don't see the issue. I frankly like these quizzes. However, like Ptcairn states below, you can consolidate your quiz ads into one thread instead of multiple. But again, it's not like you're doing it every 8 hours or something, so I don't see any issues.
message board shouldn't be all adspace btw, I suggest doing what Lindwyrm did earlier and create quizzes before advertising them all in the same thread.
I'm just not sure how groups work