The market dominance of Apple's iPod music player is causing ever more restrictive digital rights management (DRM) technologies, argued Cory Doctorow, a fellow with the Electronic Frontier Foundation. 

Makers of portable devices have different reasons to embrace DRM, Doctorow said in a keynote presentation at the Red Hat Summit in Nashville. 

He pointed out that Apple is looking to prevent users switching from iPods to competing devices by making sure that music from the iTunes music store plays only on the iPod.

"Apple [turns] every iTune you buy into a 99 cent price tag on switching from Apple to a competitor's product," Doctorow told delegates.

"If you start with an iPod and you want to move to a Creative product and you have spent $50 on music, that's a $50 investment that you abandon."

Using content to lock in consumers is even more important because such devices have an average life span of 18 months.

In a commodity market for portable media players, Apple has no guarantee that after such a time it will still have the best and/or most popular products, Doctorow added.

Apple's competitors meanwhile are pushing for even more restrictive DRM in an effort to entice content owners such as movie studios and record labels to sign exclusive content licensing deals.

By offering to further tighten DRM restrictions, such companies are playing to the content industry's fears of new technologies and piracy.

They also bank on the content owners' troublesome relationship with Apple which has shown little willingness to raise download prices.