Summary:
- The martingale strategy asymptotically implies infinite capital or infinitely divisible stake. In reality you have a limited capital and there is a lower (in casino also an upper) bound of the stake.
- In a fair game (with 50/50 chance of profit and loss) the probability of profit after a series of losses is still 50% (because the outcomes of bets or trades are independent from each other).
- Typically, if you win then your profits are moderate but if you lose, the losses are severe (you can lose your capital just after a small series of unlucky bets).
- If you make pretty many bets, you might make a good profit but the probability to make profit at all decreases with the number of bets. Losses stays severe.