It'd probably be monopolistic if they blocked IE8, and maybe IE7. But I think IE6 is legitimately old enough, with enough known problems, that it would be justifiable if it ever came up in court.
It' doesn't take much for Google's web search to support an outdated browser since it uses minimal javascript, so Google will only lose out by blocking IE6.
Not necessarily, I finally dumped my hotmail account when it told me it doesn't support Chrome.
I believe brand familiarity would carry a lot of people into using a different browser. Google did huge things by implementing the Firefox download links. If you go to google.com and you get prompted "Runs best with Chrome" and you get a slightly delayed service, people will switch. If they slowed the service down until its still faster than MSN, Ask and Yahoo, but slower than google's supposed to be, you'd be able to force many people over to the browser of your choosing for speed.
Also Bing doesn't work particularly well. It also complains at me because I'm using Chrome.
I finally dumped my hotmail account when it told me it doesn't support Chrome.
So you chose to switch e-mail providers rather than browsers. The parent is saying the same holds true for search engines, which have a lot smaller barriers to switching services.
Not to suggest that people are evangelical about using IE6 but wouldn't your example make the case that users would rather switch services than change browsers? Anything to reduce IE6 usage is good news to web developers though.
