Web of trust has been working between humans for over a million years. If we've failed to make computers do it, it's probably just for lack of trying.

To your second point, that might be true in a world where the consequences of making a bad trust decision was some kind of hassle related to changing passwords or reporting your cards stolen. But we seem to be moving towards a world where it lands you in a detention facility or some other dire consequence. I think that sooner or later, users are going to realize that they want that control and will be willing to do the corresponding trust hygiene work. Besides, isn't making that kind of work easy the point of technology? We just need to do better re: making it usable rather than investing in systems we know to be unsafe.

Humans are generally considered to have been around for only ca. 300'000 years.

Also, the interpersonal web of trust is IMHO quite clearly failing in the age of mass media, and not just recently.