It depends on your audience, and whether the cost (development, maintenance, opportunity cost of developing to a 7 year old lowest common denominator) is worth it to gain those IE6 viewers.
Also worth asking - is the IE6 demographic likely to care about or use your site? I think a large amount of IE6 users don't care about new technology (duh) or are accessing the web from corporate networks which restrict browser installations. Maybe those viewers aren't worth the effort - only you can answer that.
I was happy to see that Apple's Mobile Me site won't support IE6.
