I suspect the paywall protected articles that Google runs across aren't protected by IP address, but by User-Agent string. I've seen a few hacks for this (look

I suspect the paywall protected articles that Google runs across aren't protected by IP address, but by User-Agent string. I've seen a few hacks for this (look at the NYT User Agent hack), and the FF plugin that allows you to alter your UA string indicates this similarly. Put another way, I don't know if Google necessarily has registered all of its crawling IP addresses. Sure, you could do a reverse IP lookup -- but you'd have to do that on every request, which can get expensive. No, the cheap-easy route is probably something as mundane as UA string.