Sorry but you really don't understand the current situation. Those who still use IE6 either do so because they don't want to upgrade (or move to a different browser) or can't (because of enterprise or government restrictions and upgrade protocols). Claiming that people on old computers can only use old versions of IE is redundant as Chrome and Opera (and even Firefox) require less memory, use less resources and work to a better extent. Claiming that people in third world nations only have dodgy old infrastructures is also quite discriminatory and uninformed. Many third world nations (India would be a prime example) have put a LOT of money into infrastructure to educate their citizens in order to give them work in the future (which is also why India and China are now major players in the web sector).
I disagree, back in it's day it was a good product, but times have moved on and unfortunately a lot of governments and corporations haven't (which is rather amusing to think that our national security and customer details may be in the hands of people using such a redundant and bug ridden browser). As for the worst product, my money goes on Microsoft Bob... the VB5 written monster behind both Clippy and the "smiley" nerd emotion in MSN Messenger.
I agree, in fact, we would probably remove IE6 at a faster rate if people would just stop supporting it (to avoid reinforcing the reason not to upgrade).
Agreed, though conservative estimates are much higher than that. According to independent research provided by the likes of NetApplications (amongst others) it averages out that IE6 may still have 16.18% of the total market share. Note: that these stats aren't for Facebook but of the web in general. Scary!