Ok, say I play only on the 2:1 outside the grid spots (Black/Red, Even/Odd, 1-18/19-36). Lets say I bet $100 and lose it,so I'm -$100. Then if I bet $50 on one of these spots, I either will win and be even with where I started or be -$150. If I lose, then I bet $75 and either win and get back to where I was or go -$225.
If I keep employing this strategy, I will eventually will get back to even. Once I get back to even, I'll bet the $100 and and eventually I'll win and double my money, in which this becomes my new "even" and I repeat the strategy above until I'm a millionaire.
This same idea could be used in blackjack. Can anybody tell me why this isn't a good strategy?