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).