Google's page has toxic and false anti-AGPL FUD like this:
"This viral effect requires that the complete corresponding source code of the product or service be released to the world under the AGPL license. This is triggered if the product or service can be accessed over a remote network interface, so it does not even require that the product or service is actually distributed. Because Google’s core products are services that users interact with over a remote network interface (Search, Gmail, Maps, YouTube), the consequences of an engineer accidentally depending on AGPL for one of these services are so great that we maintain an aggressively-broad ban on all AGPL software to doubly-ensure that AGPL could never be incorporated in these services in any manner."
Daniel's explanation doesn't have false FUD like this. It has reasonable legal analysis of the effect of AGPL when you have a large labor pool, which is in-line with everything else Eben, I (not-a-lawyer), or any sane lawyer would say. It's a simple distinction.
Google lies that if you so much as touch the AGPL, you risk your business imploding and the end of Google products like Maps, GMail, etc. which suddenly become open source! That's really scary! That's a lie that scares a lot of people.
There is no "viral effect" -- that's smear language designed to scare people about having a commons -- there's a share-alike. And that implosion cannot happen -- it's simply not the result of a copyright violation. It doesn't take Eben or Daniel to tell you that. If you make an accident, the worst-case outcome is you pay damages. Damages aren't a trillion dollar punitive thing -- they're designed to set things right. You pay either:
* Statutory damages (peanuts for Google)
* Profits (how much you would have made if you hadn't used the AGPL code but e.g. licensed the code otherwise)
* Damages (how much the other party lost due to your use; typically zero)
And a little bit of engineering work to remove the AGPL stuff so the violation does not continue. Then you move on.
AGPL provides no dangers beyond those of normal, licensed commercial code. If I pay for five licenses and accidentally install ten, or similar, the exact same thing happens. The AGPL is careful NOT to explode as Google describes, exactly for this reason. It's a simple rights grant. If you do X you can do Y. If you don't, that doesn't mean I can suddenly force you to do X; it reverts to traditional copyright.
There are decades of GPL enforcement actions out there, so the no precedent stuff is nonsense too; you don't need to go to a Supreme Court to understand how these things behave in the real world. It hasn't gone to a court of appeals precisely because it doesn't need to. There is little unsettled law here.
There is a little bit of ambiguity about where the line for 'derivative work' sits, but it's also not the sort of scary thing Google makes it out to be. There is some case law around this as well, just not around the AGPL. It's not rocket science to translate.
Google is trying to kill an open ecosystem, adopting exact tactics from Microsoft's nineties-era anti-Linux playbook, right down to adopting the exact same mean, dirty language to scare people. That's a nasty, dirty thing to do.
(and in the meantime, Microsoft became, by some metrics, the world's largest open source contributor; how times change!)