You are making an excellent point that I have tried to explain before several time in answers at http://opensource.stackexchange.com
I made a new detailed QA there and I quoted you and this article: http://opensource.stackexchange.com/questions/5003/agplv3-source-redist…
The key point is that AGPL's "network copyleft" is triggered by conveying. And using unmodified (even in a public web app) is not conveying but at best merely propagating and is in this case the copyleft is not triggered. This is a subtle but essential difference IMHO.