Web-of-Trust fixes most of the "trust" issues raised (ha!). If a 100 people archive a web page and one archived version is different, the one version might be a forgery.
If people who are "enemies" in the WoT sense have the same version archived it's pretty likely that it's legit.
Yes there's Sybill attacks and other issues blablablabla but I'm pretty sure it would work in practice, and it would work pretty well.