They've made a distinction between 'friends' and 'fan' etc. pages. It seems logical that providing a full/friends-only/fan-page-only set of feeds would be a good way to manage spam, with the existing ability to unsubscribe from fan/friend pages. With all the resources and experience at their disposal, you're right, it's a bit ridiculous to suggest there's no way to avoid killing usability/usefulness without satisfying both users and companies.