Yea, this is Apple's biggest failure. They just can't seem to get and Keep quality content very long. Right now its not too big of a deal as other providers are in the same boat. But if apple really wants itunes and apple tv to be dominant in the future, they are going to have to start making some concessions to increase their content.
I've also never understood how you can Rent in HD, but only buy in SD. Why would anyone in their right mind buy a crappy, SD download? I'll just go to the local store, and buy a standard DVD and upconvert. I dunno, if your gonna offer HD, offer both to buy and rent.
They also need to start offering HD for TV shows where it actually matters (ie, not the office)...Channels like Discovery are the ones that really need the HD content.
Don't get me wrong, I love the apple tv I just bought. But a 3rd party hacker outfit (boxee) is the only reason. Without boxee, the apple tv is a waste.