iPhone developer Pumpkin plugged "rental" into a string search of the iPhone's lockdown daemon file—which authorizes the iPhone for services—returning a curious set of hits:
pumpkin:~ pumpkin$ strings /usr/local/share/iphone-filesystem/usr/libexec/lockdownd | grep -i rental
trigger_rental_bag_verification: Could not retrieve FairPlayID
trigger_rental_bag_verification: Could not initialize FairPlay context
trigger_rental_bag_verification: Could not verify the rental bag response: %d
load_rental_bag_request: Could not retrieve FairPlayID
load_rental_bag_request: Could not initialize FairPlay context
load_rental_bag_request: Could not generate rental bag request
There are actually a few more lines of code, but you get the point. If you recall, this is the second set of code that's been found pointing toward upcoming, or at least potential, video rentals.
The "could not retrieve FairPlayID" lines are probably the most interesting, or at the least ones begging most to be read into, since a rental setup with auto-suiciding content would require a variation of the current FairPlay scheme. On the face of it, it looks like the content's gotta be DRM-okayed with a kosher FairPlay ID as it's loaded.
The more relevant FairPlay DRM question for rentals is what kind of restrictions we're looking at. Rumors popped up this summer Apple was chatting up studios, which the Hollywood people confirmed. But they also confirmed they told Apple to take a hike, since they wanted more stringent rental windows, crippled portability and a higher pricepoint.