@chug: The next map isn't the only factor though. You need to keep in mind the current time and how well the previous map went. After 3 steamrolls in a row, even badwater kills the server.
Worth looking through the gameme stats on maps on this one. Last couple of weeks have seen Granary and Badlands voted in at 10 or so and promptly slash the server population. Somehow, koth actually revived the server a couple of times