That's uncompetitive, everyone should just get the browser they like either it is IE9, Chrome, Firefox, Opera or Safari - they just need to get rid of IE8/7 and PLEASE ie6.
People using IE6 are XP users considering the default browser on Vista and Windows 7 is either IE7 or IE8, and XP doesn't support IE9.
When Microsoft itself started a campain against IE6 (http://www.ie6countdown.com/) users should do a small lookup over all those other updated browsers for XP.