I'm wondering why nobody has created a review network where it only shows you reviews from someone you're connected to. Reviews would be sorted by the number of degrees of separation. Bot accounts wouldn't work because you'd need someone to endorse the bot account, and if you endorse a bot account it'd be easy to end up on a user blacklist. If you endorse someone on a blacklist then people who endorsed you would be warned and asked if they want to disconnect from you. Of course there's tons of different ways to implement the propagation of positive & negative feedback re: trust within the network.

Is it just the network effect? Would piggybacking off established social media networks not work?