Well, in our company, we have a strict policy of "no plugging in until IT has been and visited your laptop and given you the thumbs-up", and we've had this policy approved from the highest level downward.

Which is just as well; we take a copy of our latest AV software and virus definitions, install it (if it's an "alien" computer) and then scan it. We've seen Nimda, Code Red, The Klez, BugBear and so on; we've seen laptops with three different versions of antivirus software installed at the same time, all out of date and non-functional; the list goes on. [edit: Not laptops that are part of our herd, I hasten to add; these were visitors]

What enabled us to take this idea to management was the fact that we got hit by Nimda. It clobbered an intranet web server before the virus definitions were out. We were offline for 1.5 days. Management doesn't understand "Viruses are bad" but it does understand "150 man-days lost".