Google's opt-out position is exactly the right one. If we were to wait for publishers to opt in, only current, in print works would get into the index.
I think he's almost certainly right. Because inertia and fear of losing control of their IP, most publishers would probably think it simpler and safer to do nothing. However, as I commented earlier in the Internet Library situation, it hard to see the legal significance of providing an opt-out mechanism. The sort of archiving that Google is doing may or may not fall under fair use (I don't really have an opinion on that, but let publishers opt-out is just a courtesy. Here's what an expert has to say (The Patry Copyright Blog--a great, if very detailed and technical source, for copyright discussions):
The legal issue remains the same, however: whether copying of an entire work without authorization is an infringement where the ultimate user is able to see only a few sentences of the original. Since fair use is an unconsented to use, the fact that publishers object doesn't matter, regardless of the chutzpadik way Google may have handled the issue (The Second Circuit is divided on whether bad faith is a fair use factor). And whether Google is actually an advertising behemoth that doesn't want its own service to be used to investigate itself, whether it is, therefore, a false great white knight in the culture wars (if there are any) shouldn't matter either.