You can use a Flash compatibility shim to make your sites use Web Sockets in some browsers and Flash sockets in others: http://github.com/gimite/web-socket-js
This is the best of both worlds; Flash works for IE users, and Web Sockets will hopefully be available soon in plenty of non-Flash browsers (like the iPhone).
I think the main issue here is not IE6 but all the modern browsers (FF 3.5, Safari 4, IE8) that do not support this feature. Targeting Chrome users only is not that appealing.
While the numbers are falling, IE 6 users still account for a sizable percentage of the people that buy things from my site. Ignoring them would be "doing something wrong". Guess it just depends on what you're doing.
Also in case you are doing something that spreads virally, not supporting IE6 can change the viral loop from increasing to decreasing (you could lose 5% of invites/feed messages/emails/whatever depending on app).
I recently did a bit of consulting work for a guy who has a large number of domains receiving primarily organic search traffic. Around 20% of the people hitting those (several million a month) are still using IE6.