From the ITIF website...
"It is my hope that with this alert ITIF will be able to remind people how easy it would be for sites to block users who enable Do Not Track..."
I really can't see any website that makes direct revenue from users would block access. Would Amazon block me if I have DNT enabled? Would they risk losing a sale on that new plasma TV over $0.03 of indirect revenue. Sure, the Amazon example is a bit extreme but seriously. I can't see any legitimate website blocking a user, and possible direct revenue stream (subscribing to, or buying from, etc) just because they are running plugins.
Is the corporate world really that insane? Have they totally forgot in the long run we are the customer and ultimately the revenue stream. Can't they see that now matter how many ads they force on us if no one is looking THERE'S NO MONEY?!?!