Statcounter isn't your site. Everyone should look at their own site stats and make the case as to whether legacy browsers should be supported.
Regardless, for new projects we still follow the Yahoo Graded Browser Support baseline, like many other agencies do. http://yuilibrary.com/yui/docs/tutorials/gbs/
I think there is value in moving to faster deprecation. Plus even if it does make finicial sense for airbnb it is still a risky investment. Should a facebook, google, or wordpress drop ie7 support hard then all the sudden you've wasted money, developer time, and developer sanity.