Consensus process (the idea that a group must strictly adhere to a protocol where all decisions are unanimous) is the absolute worst idea that has ever been introduced to the activist community.
Consensus process is the tyranny of the individual. It is the most anti-social of all processes because it allows any one person to assert irrational authority over an entire group of people and block any sort of decision making. It has nothing do with anarchism (even the IWW doesn't use consensus!) because it was invented by Quakers for religious reasons. It's stood in the way of progress, destroyed social movements, destroyed groups, destroyed communities, and relegated radicals to the fringes of American politics since the 70's when it was first popularized.
Consensus process is in many ways an attempt to formalize the act of resistance, which I suspect is what makes it so popular in activist communities. Let's compare this to democracy, a system which was invented to formalize dissent. With democracy, you could fight and disagree without resorting to violence. Feathers could be ruffled, progress could be made, and life moved on according to plan. Resistance on the other hand is when you're so angry at something, that you're willing to go on a crusade and use all available means to stop that thing from happening Resistance knows no rules. It is something that should never happen, yet is the responsibility of any socially conscious individual. It's a wild beast which cannot be tamed. Now ask yourself what happens when you get a bunch of people in one room, people whose nature inclines them towards resistance, and then give them the power to resist with a simple hand gesture and a requirement that all others be subservient to their demand. You do the math.
To give an example, the first time I saw a block used at Occupy was at one of the first general assemblies in August 2011. There were about a hundred people that day and in the middle of the meeting a proposal was made to join Verizon workers on the picket line as a gesture of solidarity in the hope that they might also support us in return. People loved the idea and there was quite a bit of positive energy until one woman in the crowd, busy tweeting on her phone, casually raised her hand and said, "I block that". The moderator, quite flabbergasted asked why she blocked and she explained that showing solidarity with workers would alienate the phantasm of our right-wing supporters. Discussion then abruptly ended and the meeting went on. The truth was irrelevant, popular opinion didn't matter, and solidarity—the most important of all leftist values—was thrown to the wind based on the whims of just one individual. Occupy had to find a new way to do outreach.
But as bad as that sounded, it was actually one of the most graceful instances I've seen of a block being used. This is because the proposal was actually drop