A vendor has a release out talking about how the biggest problem for wireless networks at the recent DefCon conference was not all the hackers doing jamming, de-authentication, denial-of-service, and so on. Instead it was interference in the networks themselves from non-Wi-Fi sources:
“We were more surprised to find that an abundance of Bluetooth devices, microwave ovens, 802.11 frequency-hopping devices and Web cameras were more effective at knocking out the conference’s wireless network.”
As the release goes on to say, data-centric wireless nets can handle this sort of thing reasonably well, but get a few isochronous apps running — like voice and video — and you will have all sorts of problems in any real-world environment.
They have a neat screenshot of some of the sources of interference here.