That sounds like a terrible idea. You think every end user, everywhere, needs to manually verify with their ISP for every single outbound connection? How could that possibly be an acceptable solution?
I think you misread or misunderstood what I meant by "blocking significant outbound traffic". 99.9% of what home users do doesn't generate significant amounts of outbound traffic. If someone typically browsers the web, sends a few emails, and then their traffic starts doing 20Mbps/s on an undocumented port, blocking that traffic until they verify what it is wouldn't be a bad idea. It wouldn't affect most users.
