I presume Google's goal is to reduce the percentage of IE6 users down to levels where consumer-oriented sites don't think it's worth supporting anymore? Today, IE6 is propped up by personal use of corporate machines during the workday. I worked on a consumer site where the percentage of IE6 use was higher during the workday than on nights/weekends. Various negative inputs into the IE6 ecosystem feedback loop could cause a precipitous death spiral.