How Google did it is that they manually picked a number of websites that they considered trustworthy and gave them a high reputation.

Looks similar to how Ripple is decentralizing their validator nodes. Their UNL started as a 100% ripple nodes list, then they replaced one ripple server with a "trustworthy one" (on their own view) at a time, until the ripple owned servers became the minority of consensus.

Someone with a high reputation adding a link to another user means that this second user's reputation increases. Whereas if a low-reputation user adds a link to another user, it doesn't make much difference.

I like this idea, seems like the decentralized version of what Ripple or Google did. I see a good potential on that idea, if a good developer takes it.