You might have read about the military banning portable drives, this today from a senior anti-virus researcher for Kaspersky Lab:

Tons of USB devices are leaving the manufacturing plant infected — Seagate, TomTom, Apple to name but a few of a very long list. Again, this is very reminiscent of the boot virus era where new pre-formatted floppies had quite a good chance of being infected with something.
So what are the mitigation strategies? Well, using policies you can disable the AutoRun functionality. That will obviously take care of the biggest part of the risk. But the risk remains of users being curious about that one file on the device - either because it’s new from the factory or because they can’t recall putting it on there and want to check what the file is. Another strategy is formatting the device before use, but that may not even be possible in most cases. I think the real solution is with Microsoft, just like with the boot viruses.
http://blogs.zdnet.com/security/?p=2235