Turning Turbines

How much control does the wind have over a turbine?

Last summer, I was on a drive through the country where there was a ton of them and not all of them were spinning.  Some were and some weren't, and from what I can recall the ones that weren't had a red light on at the top.  However, the stopping seemed intermittent so I know it had nothing to do with some sort of malfunction, and the fact that others in the same area were turning means there was enough wind available.  Also, a smaller turbine had been setup recently at a GO station not too far from me and I've seen it turn wildly on a windy day to then suddenly stop. So I don't understand.  I thought the whole point of these were unabashed energy production, i.e breeze/wind = power, not specified hours of operation. If that's the case, and the turbines are limited in what they can produce in whatever means I don't really see the point. That would be like having a solar panel face away from the sun on a really sunny day for a certain amount of time. Shouldn't the goal be to get everything we can from these natural sources?