Do they have some special arrangement with the companies in question?

My brother has a business DSL line, and that was enough for Hulu to decide that he's using a proxy and block him. They've repeatedly called support and support repeatedly told them to "stop using your proxy" (despite the fact that they are using no such thing.) So Hulu isn't at all afraid of false positives, and that kind of blanket ban should be effective unless unblock-us has a deal of some sort worked out.