This seems to be an unspoken policy change. I'm joining the outrage bandwagon now.
> What's infuriating is Apple's inconsistency. Some apps offer subscriptions outside of the app store and are still there (including Basecamp!)
That doesn't violate guidelines. Unless your app takes users outside of the app store to purchase stuff(including the subscription itself) without in app purchases.
Having an app requiring login is ok. It doesn't matter that the login is protecting a paid service.