Review of reviewers is totally the way to go! It sounds like a "now you have two problems" situation, but it really isn't. Starting from the one reviewer of reviewers you know you can trust (yourself) you can build out to a network of trusted reviewers.
If anyone's interested in working on open source solutions to this problem, feel free to email me. It's kind of my thing:)
Funny you mention this because a friend and I were sick of video game review sites leaving obviously paid for 10/10 reviews (here's looking at you, Eurogamer). So we put together plans to build a "review the reviewers" website where people could leave feedback on a particular reviewers integrity, honesty, trends and so on.
We never did finish it but I have lots of code, docs, ideas and research from that time and I'd be happy to help with your idea if you pursue it.
Yeah, a web of trust style weighting of friends-of-friends-of-friends isn't a bad idea at all. Current social networks doing that sort of thing tend to only care about immediate friends, which is only very narrowly useful. Good luck with your project.
If anyone's interested in working on open source solutions to this problem, feel free to email me. It's kind of my thing:)