Let me put it this way: the Revolution in and of itself will screw the movement over. A mob mentality ultimately takes over, and even people sympathetic to the cause get thrown out, and soon, someone charismatic comes along and takes advantage of it all (Napoleon, for example) and then things don't go great.

granted, Russia DID see some gains from the revolution, but there's a reason it only happened in places lagging behind rather than the places marx predicted: the serfs were so held down, they had absolutely nothing to lose by revolting, no matter how horrible the next regime.