Apple was just awarded a patent for their iPod media player. Even though it has been available since 2001, they have only recently been able to grab the patent for their multimedia device.
This may also have a lot to do with some patent disputes in the past. As with any major company, there are always a few people sitting around on random patents just waiting for someone to make some big bucks on an idea.
Other times, there are legitimate companies that mean to protect their intelectual properties. Unfortunately, patent law in the US seem to be more of a hinderance than a help.
As you look at the images take into account the last bit of this claim:
It we are interpreting that correctly, that means only a rectangular shape and the scroll wheel are part of their design.