If you have an unlimited bankroll with no betting limits theoretically you can dig yourself out of a hole if you go on a ridiculous losing streak on the martingale system.
In reality though, using the martingale system on any type of gambling carries risk because not everyone has an unlimited bankroll, and many betting sites or casinos will eventually limit your stakes.
Every casino will eventually limit your stakes. There are only ever going to be 21 million Bitcoins. It only takes 25 doubles to get from 1 BTC to over 21 million BTC. People don't have a good feel for how quickly "doubling" makes a number big.