Hulu made a subtle change to its iPad app this weekend, cutting off that bottom line you can see in the screenshot above. Yes, per Apple's rules on charging for in-app subscriptions, Hulu can't actually link to its own site to promote its own subscription service for video streaming of TV episodes, movies and such.
Apple's rules say either no links whatsoever to outside subscription signups, or both in-app subscriptions (which means a flat 30% goes to Apple directly) and offsite links. Since Hulu doesn't want to give any cut to Apple, the choice has apparently been made to simply offer the app as a service itself, rather than an ad for the site subscription.
Will this affect Hulu's sales? Probably not too much -- I'd assume that most Hulu users are already subscribers, or at least know about the option already. Clearly the company determined it was more important to get the app out there than to worry about using it as an advertising tool.
We'll have to wait and see how (or if -- some companies have already confirmed that they won't be dealing with in-app subscriptions at all) other subscription services handle Apple's restrictions.