> Google serving your pages?
Yeah, what's bad about that? It is, actually, a feature of a free open web: content is there, available to anyone, including Google, to be rehashed, kept, reserved, in anyway any one see fit.
Wikicache is a feature of an open web, that does a very similar thing to what Google is doing.
> Use of a proprietary technology (whether open sourced or not, it's not a standard)?
We have really come a long way if this is what we now call a proprietary technology. My understanding (but I could be wrong) is that the specification is open, everyone is free to implement it, fork it, make editors or readers about it.
Proprietary implies (or used to imply?) that some of these rights are limited: the MPEG consortium forbidding encoders without acquiring a proper license, Oracle claiming that you can't make a Java VM without making an agreement with them, etc...
My understanding is that AMP is as open as it could be: it was just proposed by a private entity. Criticism is a good thing, but saying it will break the open web is simply a warning I can not understand.
If something needs to be criticized, it is Google's quasi-monopoly on search, but even that is not that much of a threat given how many of its competitors are still easily accessible from any device and out there to gain a foothold as soon as Google's search results show any kind of weakness.