> On Firefox, which blocks third party cookies, I have to log in to each of those domains separately. I can't log in to stackoverflow.com, then go to superuser.

> On Firefox, which blocks third party cookies, I have to log in to each of those domains separately. I can't log in to stackoverflow.com, then go to superuser.com and already be logged in. That is a problem that First party sets would solve. The cure is worse than the disease.