In my previous post, Consensus over Compromise, I was probably overly enthusiastic about consensus as a way to reach agreement. I'll expand on the drawbacks in this post, as well as mention some ways to combat the problems.
Patience and Persistence
Consensus is frequently a slow process and gives undue power to those who have a lot of patience. On the other hand, this is probably true of many decision-making schemes; being persistent, even nagging, will often result in you getting your way during attempted compromises and informal votes.
If there seems to be a consensus on some issue, it may be difficult for dissidents to come forward, not daring to mention legitimate concerns. This is probably particularly true of shy people.
Consensus assumes minimal trolling. Those who raise concerns that have already been extensively discussed and addressed are detrimental to the process, and if there are too few moderators, they may effectively have veto power.
Nowadays it is common to use bots to affect public discourse, and they may make it seem as if everyone agrees on what actually is a minority opinion. In a podcast with Renée DiResta, she describes how polls suggested that 85% of the inhabitants in her state support mandatory vaccinations, while any online forum overflowed with anti-vaccination groups and posts.
It comes down to having competent moderators, who have an overview of who is taking part in the discussion, and of whose opinions have already been addressed, or not heard.
Knowing who is a troll or bot can be very difficult online, but it's crucial that moderators don't take too much consideration of people who don't respond at all to arguments, and instead focus on given concerns and whether they have been sufficiently addressed or not.
Do you know of further drawbacks or solutions? I'd love to hear your ideas!