Hi, I want to make some kind of an ongoing quiz on a social network like Gather.

I think of asking a question, that can be commented upon with answers. Rules are, that you have to improve the answer, and yet leave room for another improvement.

Example:
Q: Larger city

Comment 1: Boston
Comment 2: Chicago
Comment 3: New York
Comment 4: Mexico City
Comment 5: Tokyo

Comment 5 looses - it is not possible to improve, since Tokyo is the largest city in the world, no. 4 wins - improving no. 3 and leaving just enough space for no. 5.

Any ideas for questions? Thanks in advance.