I though it was getting to a point now where IE6 support was more for intranet and business sites. Is it a case of everyone supports it because everyone supports it, or people still use IE6 because it's supported?
I mean, if you "don't support" IE6, what is the worst thing that happens? Some stuff doesn't look right for a portion of your audience? These people already have a seriously degraded internet experience, are they going to notice that the padding on your floats is all messed up?
I am pretty certain that you are leaving revenue on the table if you choose to ignore IE6 as a business, which is a valid objection to my argument. But how much?
And how much costs are you leaving off the table by freeing your designers and developers from supporting IE6, and allowing them to do other amazing things with their precious time?
Give me two almost-identical websites with two similar, business-oriented audiences, then have one site support IE6 and the other basically ignore it (and use the excess development/design time to build other features). I don't know about you, but I'd put my money in #2.
How relevant this is to your income, of course, depends on the site. For a blog, it may not matter at all, but there's a good reason why Facebook is notifying IE6 users of a degraded experience. They use a ton of CSS/Javascript for their UI, and I'm sure the cost of supporting IE6 is very measurable and very high. But they probably can't just tell IE6 users to go away entirely.
Does Windows normally offer to upgrade IE automatically?