> How about publishers serve ads from their own main domain ? ...

Yeah, I'm a big fan of the idea. Imagine this - what if advertisers would give you a small PHP script to include in the website source code, that would run random code on the server, instead of ga.js? Would they think twice before including that crap? I bet they would.

As it stands, I've encountered sites that wanted me to run even 10 different scripts on a page, for ad networks I haven't even heard about.