Except someone like Google would likely also want their site to work, and thus I expect them to be unwilling to use such a problematic IP. If any big site (or

Except someone like Google would likely also want their site to work, and thus I expect them to be unwilling to use such a problematic IP. If any big site (or even better, many big sites together) were willing to go that far, a much better measure would be announcing that they'll go IPv6-only on the next IPv6 day. Just for that day. And then again the next year, but for a week. Then for a month the year after. Then permanently. That would give ISPs the kick in the butt to fix it, because nobody wants their hotline to field a day full of "my Internet doesn't work" calls, only to then have to fix it anyways because otherwise it'll be a week next time.