Regarding your first point Matt is talking about 'community' in the context of one of these front end sites that displays content curated for that community. If THAT community doesn't like someone they can turn on them. That person can then just go and find another group. Groupthink only really applies when there is one giant group. When you have the big group broken into thousands of smaller groups all with the same power the problem reduces greatly.

As for your second point, Matt would have to address that one.