Can't remember the name of the manufacturer, but there is one drive that has a write protection tap which is quite smart...
If you're ever infected by a virus, just use the pendrive on another system, load it up with the antivirii programs you need, write protect it and connect it to your own computer... You'll be rid of the virus, and won't have to worry about wether the drive got infected or not...
So I'd look out for a drive with this feature..
.02$