Earlier quoted context omitted.
I work for Google but not on search. I think in this case semantic web would not work, unless there was some way to weed out spam. There are currently multiple competing microdata formats out there than enable you to specify any kind of metadata but they still won't help if spammers fill those too. Maybe some sort of webring of trust where trusted people can endorse other sites and the chain breaks if somebody is fou…
In the interests of not causing a crisis when Top Level Trust Domain endorses the wrong site and the algorithm goes, "Uh uh," (or the endorsement is falsely labeled spam by malicious actors, or whatever), maybe the effect decreases the closer you are to that top level. But that's hierarchical in a very un-web-y way... Hm.
And that has worked... quite fine. I have no objections (maybe they're a bit too liberal with the new TLDs).
Most of the stuff that makes the hierarchies seem bad are actually faults of for-profit organizations (or other unsuited people/entities) being at the top, and not just that someone is at the top per se. In fact, in my experience, and contrary to popular expectation, when a hierarchy works well, an outsider shouldn't actually be able to immediately recognize it as such.