My guess is the majority of IE6 users these days are due to a large number of companies/organizations that are stuck with illogical browser upgrade fear.
I work as a contractor for the US Government and, as of the time of this post, the entire Heath and Human Services department of the US government is still standardized on IE6 (and doesn't appear to be planning on upgrading anytime soon). When I ask the IT people about it, they claim it's too expensive for the government to test new browsers for compliance with security standards, but I get the sense the real reason is they are afraid of having to deal with things rendering differently across browsers.
