As with anything, it's a cost/benefit analysis. If you ran a company that sells a billon dollars of products online per year, would you ask your web developer to spend hours ensuring the site looks and functions decently in IE6 if that means an extra $26 million? I sure as heck would.
On the flip side, if you're short on resources and that time would be better spent adding functionality which would result in > 2.6% return, then by all means ignore IE6.
On the flip side, if you're short on resources and that time would be better spent adding functionality which would result in > 2.6% return, then by all means ignore IE6.