"Linux," said the salesman. (He was ever so helpful.) The next question, "Does it come with anti-virus?"
That certainly stumped the salesman. He answered a non-answer, really. "Linux," he said, "It has Linux anti-virus."
For the record, the Eee, which runs a form of Xandros, does in fact have anti-virus. We are pretty sure the reason for this is two-fold. One, it puts some people's minds at rest to have something called "anti-virus" on their computer. Two, it does isolate and quarantine viruses -- viruses that might not affect Linux itself, but could easily be passed on to a Windows machine.
That's not to say there aren't viruses that can target Linux.