Is the question/answer something you made up yourself? If so, it will indeed keep the spam away.
I also agree in the users without posts. I would even agree to delete users with 1 or 2 posts. Would you care if your account on a forum got deleted where you posted 2 messages? I wouldn’t.
Edit: I did a quick check. Deleting all users with # of posts <= 2, the user count would lower to 21 pages.
Deleting # of posts = 0 would equal 46 pages. As the # of members is spread over almost 500 pages, I guess we can delete quite some users. 🙂