what I do when exploring any game concept is to quickly prototype a playable version, and try to "find the fun" in the game. Once a certain fun level is reached, iterate, and build the game around that.

to see if people actually want to play the game, you need to test the waters. Ghetto-like testing (Zynga's much publicized way of using FB game ads to gauge user interest ) is one option.

Fun = addicting game mechanic.