Another point here about microwave ovens is that the reason that they were assigned a specific frequency is because they can and do cause interference, so they needed to be assigned a band to cause interference in that wouldn't interfere with anything else assigned at the time. And if I'm not mistaken, the reason that no license (and associated fees) is needed to use this frequency is because no quality of service can be guaranteed; it's already assigned to "noise and garbage". And people wonder why they have problems with WiFi. But hey, at least it's cheaper!