It appears that antivirus companies have begun to sell their products on USB thumb drives. This is a great idea now that Netbooks are more common since many of them don’t have an optical drive. In fact, some antivirus companies such as Panda Security are making a Netbook specific versions of their antivirus products which are lighter on resources and come on a USB drive.
Another great thing about antivirus products coming on a USB drive is that the installation of the antivirus product (which usually takes ages) would happen much faster, since it is usually much faster than installing something from a CD.
Lastly, at the end of the day the customer is left with a USB drive which they could use for other purposes.