iPods and MP3 players are consumer electronic devices that are totally separate from the corporate sector. IT departments have enough to worry about without going out of their way to find new topics about which to get neurotic.
The fact that one model of iPod has been found to carry a virus that affects Windows is worthy of note. The bigger point is that there is no dividing line between consumer and business electronics. None at all.
There always has been an overlap between business and personal electronics. It's assumed that people make personal calls from work on their business phone, for instance. In the vast majority of cases, such use is accepted as long as it doesn't get out of hand. That tradition has extended into the era of advanced electronics. People have lives, after all.
But mobile and wireless computing increases the inherent risks of dual consumer and business device use. For instance, one of the biggest concerns of IT security folks is that a work group or department will buy a consumer access point at Best Buy or CompUSA and plant it on the corporate wireless local area network. They think they are increasing efficiency. However, such devices often are invisible to the IT staff and don't have enterprise-level security -- they are called consumer devices for a reason -- and represent a risk from the moment they are turned on.
It gets even more risky when employees leave the building. In the real world, just about everybody uses their mobile devices indiscriminately for work and play. This is a big deal, even for the vast majority of people with no ill intent. The problem will grow even more daunting as the capacity of removable storage media grows. Users' Ray Charles and Grateful Dead tunes will be mixed with the month's sales receipts and customer contact information in a horrifyingly insecure potpourri of data.
The fact that Apple has a virus problem is a red flag. Unfortunately, the policing of these dual-use devices is very difficult. It's simply hard to control what a person does when he or she is out of the office. The subject is even touchier when companies ask employees to use their own devices for business.