Some pretty major changes between IE8 and moving forward. I have to maintain support back to IE7 in the websites I make at my work, and its painful in how this limits what we can do. But those pain points don't really start to go away until IE9... and when it comes to HTML5, I'd love it if we could cut support at IE10... It'd reduce a LOT of trouble spots we have.

If I were running a fansite, I'd gladly toss older browser support out the window. Especially as most of the holdouts for old browsers are those large IT departments at companies - and cutting fansite engagement for people at work... not as hard a calculation to make (though it can be significant).