A trust network can certainly be an echo chamber. Many people today foolishly design their trust networks as an echo chamber because they prefer to avoid information that contradicts what they believe to be true.

There's certainly nothing about using computers that will force people to accept information from diverse sources, for example. But computers could help you analyzethe network you're building and at least let you know that you're narrowing your sources of information. They could also inform you in cases where the vast majority of people disagree with the opinions of your trust network. What you do with that information, as always, is up to you. But if you find that your trust network is rating a lot of information incorrectly (in the sense that you find it giving a lot of wrong answers in cases where you're able to verify the truth independently) you may be incentivized to change your network in a way that makes it more useful.