Apparently these things are rigged. *shrug* These games have settings that are controlled by the vendor that change the difficulty of winning the highest prize, which is usually something like an iPod. Basically any time something is won, difficulty is ranked up to max, which gives you the very smallest fraction of a second to press the button correctly. After many, many consecutive losses, the game lowers the difficulty ever so slightly.
By that logic, you can eventually win. If you see a $100 iPod and think you're skilled enough to sink $20 in to attempts at winning, by all means go crazy.