Negative Progression roulette

[outdrwn]

I think I have found a system that could make anyone money, playing roulette. Just pick a color, put down a bet of...200 bucks(or w/e is within your bankroll, which should be about 100X the size of your initial bet). If you win your bet, you quit(profit 200 bucks, from 1 lucky coin toss, basically). If you lose, you bet 400. Win, quit, lose, bet 200+400+200=800. Win, quit, lose, bet 1800. Etc.

Why doesn't everyone do this? Im sure there are plenty of online casino's that would have you even if u did break every casino in vegas regularly. Is there something I'm not seeing?

thanks...