It's weird: you'd think all your top JVs would have enough cash already, and yet, large cash prizes are usually very effective.

Fancy toys (xBox 360, Wii, iCrap [erm...I mean iStuff], laptops, etc.) work alright in the IM space, but after a time, you'd expect everyone to already have most of these things. And outside of the IM space, such prizes are not always appropriate.

Prizes that often work very well are the ones with cool factor or the ones that elicit a "holy freaking crap" reaction. These are prizes that people would probably not think of buying for themselves, even if they can (easily) afford these things. For example, most people would never consider getting things like rides in fighter jets, vintage muscle cars, premium wines, diver propulsion vehicles, or expensive cameras (DSLR, video, or whatever).

But yeah, cash works too :P