The anthropic principle gets in the way. If you play classical (i.e. non-quantum) Russian Roulette 10 times and live, you might conclude that there is some force protecting you from death. If you play classical Russian Roulette 10 times and die, you're not in a position to conclude anything much.

Assuming MWI is true, I have doubts about the idea that repeated quantum suicide would prove to you that MWI is true, as many people seem to assume. It seems to me that we need to take into account the probability measure of observer moments, and at any time you should be surprised if you happen to find yourself experiencing a low-probability observer moment - just as surprised as if you had got into the observer moment in the "conventional" way of being lucky. I am not saying here that MWI is false, or that quantum suicide wouldn't "work" (in terms of you being able to be sure of continuity) - merely that it seems to me to present an issue of putting you into observer moments which have very low measure indeed. If you ever find yourself in an extremely low-measure observer moment, rather than having MWI or the validity of the quantum suicide idea proved to you, it may be that it gives you reason to think that you are being tricked in some way - that you are not really in such a low-measure situation. This might mean that repeated quantum suicide, if it were valid, could be a threat to your mental health - by putting you into a situation which you can't rationally believe you are in!