Sure, I have a nice idea:

We can offer some cipher text (using any cipher you wish), and ask them to recover the plain text. Or anything harder that google/internet can't solve

I also think we should make the following changes :
(1) Questions should be posted at a fixed time, say 08:00, so that ALL users have access to the question before someone posts the answer quickly, 'cuz they know when the question is to be posted. With a random posting time, the one who is online at that instant is at advantage.

(2) If the answer to the question is not posted within 00:01 (12:01 AM) of the next day, the 1$ for that day should go towards the Support open source campaign of The thread should be locked so that no answers are accepted.

Please give your views.