Apple COO Tim Cook this week said "Apple will continue to invest in its Apple TV set-top box "hobby," despite its relatively low popularity." Why? "We're continuing to invest in it because our gut tells us there's something there." Yes, the "SOMETHING" is a $100b advertising market and an equal amount of money spent on content.
He continued to state they had no interest in making TVs. Double-speak. They're not going to make TV, they're going to make large computer monitors w/ an OS and chipset.
This is no different than if Apple insisted they're not interested in netbooks and then launch the ipad. They're never interested in an existing category. They're interested in creating a new product which displaces an existing category.