Distributed trust isn't better than centralized trust. In fact, it'll fail more often. It's just that the failures have varying degrees of severity.

Same principle as saying, "I will make my website more reliable by adding more servers." In fact you make it less reliable by doing so, you just change the severity of the problems.

And we've seen economic mechanisms compromise signed star-shaped trust graphs. E.g., all these atom plugins with features/spyware circulating because a small handful of companies think it's a business model. That's literally just buying the property from folks and ruining it. That's a very powerful attack against a web of trust and often cheaper than the fake cert attack, which is actually something you can guard against if you feel inclined to do so.