Another interesting article in IEEE Spectrum. The topic of the publication is a hypothetical WiFi Worm Outbreak. A research team from Indiana University ran simulations of how such a critter would spread in densely populated areas, such as New York City or downtown Chicago.

While the likelihood of such an event taking place in the foreseeable is low, the massive exposure of such a vulnerability would bring with it a huge risk for home users and business alike.
Despite the fact that we do not know of a real WiFi vulnerability that could be exploited in this way, we are aware of things like UPnP attacks that could lead to almost the same effects.
The tips are sound: keep your router protected with a (very) good password, do not allow remote administration of your device, switch off services that you do not need, use common sense, and err on the side of caution