I've experienced congestion at my parents house. They live in a rural area and have a connection over a WiMax wireless link. I did a little poking around and the bottleneck is not the wireless link but some link further upstream (e.g. maybe between the ISP and the wireless tower).

I suspect what is happening is that the uptake of video services like YouTube and Netflix has resulted in link capacity being exceeded. The result is not pretty. The link acts like it is dead for about a minute at a time. It periodically starts working for a few seconds, maybe up to a minute, but then dies again. I suspect this is the oscillation effect at work.