It's a chamber that you decide vs one the group decides.
If you want to only surround yourself with people that are exactly like you that's up to you. If you want to be an intelligent thinker and surround yourself with believable truthful people who expand your worldview that's also possible.
It puts the power back in your hands instead of the site operator or group consensus.
One of the reasons people use social media is to get a feel for the generally environment of opinion, even if we disagree with it. We want to know what "people are saying" and understand the rapidly-changing boundaries of what is socially acceptable. That's why I follow people on Twitter and Facebook that I don't trust at all. I would not want to use a decentralized trust system to consign myself to an echo-chamber, even if it is full of believable truthful people.
But the system TimJRobinson describes is flexible: you don't have to simply filter out the less trustworthy posts. You could simply flag them somehow as low-trust.
Right now the major social sites are designed to amplify the voices of users that produce content that drives engagement, even though the most engaging content tends to be offensive or inaccurate. That's why the people I least trust on Facebook always show up on the top of my feed: I sometimes engage with them by telling them I think their posts are inaccurate.
So I can see your system being used not just as a filter for what the users sees in their feed, but as a feedback mechanism for people's posts.
I think a more responsible social site would optimize for positive outcomes, and not just engagement: employing algorithms and techniques to optimize for accuracy, quality, and civility. I think decentralized moderation could be one of those techniques.
The problem we seem to be seeing just now is lots of echo chambers have formed without input from "the other side of teh argument" on Facebook, Twitter, whatever social media you choose.
What you are suggesting is rather than group level echo chambers which will validate maybe 80% of your views and go against maybe 20%, you are now going to have a fully customized echo chamber that echos your views 100%. I think that will make things worse.
Personally I try to get views from both sides, but I think I am in a minority for doing this.
If you want to only surround yourself with people that are exactly like you that's up to you. If you want to be an intelligent thinker and surround yourself with believable truthful people who expand your worldview that's also possible.
It puts the power back in your hands instead of the site operator or group consensus.