jbmagic, please, for the love of god, just read this:
http://en.wikipedia.org/wiki/Martingale_system
The best summary I can give for why this system sucks comes from that article:
People think long losing streaks are impossible, but they aren't. In fact, they are practically guaranteed to happen eventually (the longer you play, the more likely they are to happen). When it does happen, just ONCE, you go broke.
Consider that it's not even that long a losing streak we are talking about here, in most cases. For instance if you have $1000 and are betting $5 to start, you will be broke after 9 losses in a row. That streak is not that rare. Even in a coinflip game that should happen about 1 in 500 tries. It could happen the very first time you try it. Blackjack is not a coinflip game. Your chances are worse long term in blackjack than in coinflipping, so it will happen sooner than in coinflipping on average. Remember, it only takes that one losing streak, and it WILL eventually happen.