Not every video capable iPod is compatible with Apple’s new movie rentals at the iTunes Store, leaving some customers confused about why they can’t play every movie Apple offers. Other iPod owners are apparently upset over the limited compatibility, according to Wired.

Apple introduced iTunes movie rentals early in January at Macworld Expo in San Francisco. CEO Steve Jobs said during his keynote that the movies could be watched on a computer with iTunes, certain model iPods, the iPhone, and Apple TV.

The iPod models that support movie rentals include the iPod touch, iPod classic, and third generation iPod nano -- all models that don’t stream video through older docks.

While Wired implied that Apple intentionally left fifth generation iPod owners out in the cold by stating "Apple prohibits iTunes movie rentals" on older iPods, it appears more likely a technology limitation imposed by DRM restrictions. Older iPod models, like the 5G iPod, could potentially allow someone to play through to a recording device to make a copy protection-free duplicate.

Yankee Group analyst Carl Howe added "The other factor is whether you have a secure real-time clock. Why do I want a secure clock? Because you don’t want people messing with the time code since [iTunes] rentals are only supposed to last 24 hours after you start viewing them."

That may not, however, be much of a consolation to 5G iPod owners that want to watch rented movies on the go. One Apple forum poster commented "If all of the other services are available for the 5th Generation Video iPods, why not rentals?? I have a tough time believing it would not be technically feasible."

[Thanks to TMO reader MacKauai for the heads up.]