oddsod - 4:22 pm on Aug 29, 2007 (gmt 0)

it isn't realistic to expect Google to notify and obtain consent from every AdSense publisher

You're muddying the water. Individual consent for every minor change is a far cry from sending out a notice to all publishers. I don't see any reason why they can't email a notice, it would give publishers a chance to remove Adsense from their sites if they didn't like the change.