It's not quite that bad as the channel time requirements for most IoT applications are small. I did some research on this (https://github.com/hughobrien/wlan-stats) but it's far from complete.
When your wireless technology has an average outdoor range of 30-40 feet, of course spectrum is not an issue. When large numbers of endpoints (thousands or tens of thousands) share a common access point over many miles, it's a really significant issue that can be addressed in a number of ways outlined here http://bit.ly/1hExgtG