Leads to a prisoner's dilemma situation. A move like that has to be done by everyone in concert (example: killing Flash), or it's harmful to the one browser tha

Leads to a prisoner's dilemma situation. A move like that has to be done by everyone in concert (example: killing Flash), or it's harmful to the one browser that blinks first. This thread contains plenty of examples of legitimate uses for third-party cookies. If FF instantly and immediately broke those, users would be cursing, not praising Firefox, and switching to a browser that doesn't break what they use.