Apple does not currently offer to rent movies on the iTunes Store, as it is easier to maintain the store by simply selling films and TV shows, but things might change in the future according to David Watanabe, known for its software NewsFire.
While he wanted to report a problem on the iTunes Sore, he spotted on the list of potential issues "Did Not Receive - Rental Movie".
It indicates that while the Store does not offer renting movies, the system is designed and ready for supporting such function. However it remains to be demonstrated that a movie renting on the iTunes Store is financially interesting, as well as an offer largely requested by customers. So far all online renting movie stores have failed, or have trouble surviving (at least in Europe).
[translation by Linathael]