I doubt that I'm the first to notice this, but I've noticed that the "ad hoc" mode of 802.11 acts like a virus. I've been traveling internationally lately, and notice that every VIP airline lounge I go to has the same set of ad hoc networks being advertised, with SSIDs such as "Free Internet Access" or "Free Public WiFi". None of these networks worked.
The reason is that when you connect to an ad hoc wifi net, you start sending out beacons yourself. Thus, if you connect to a "Free Public WiFi" ad hoc network at the airport, then turn on your notebook on the plane, you'll start advertising that you supply a "Free Public WiFi". Other flyers greedily hope there is WiFi in the air, and will connect to your ad hoc network. When they land at the next airport and turn on their laptops, they will in turn advertise a "Free Public Wifi" that yet more people will connect to. Thus, ad hoc SSIDs that advertise free internet services will quickly spread around the world by airline passengers.
This is a benign virus, of course, but it's "viral" nonetheless.