Wind farms shut down for a number of reasons - wind isn't blowing strong enough, price of commercial power is too low for the operator's liking, no one is buying power on that grid, something needs maintenance, migratory bird season, equipment malfunction, etc.
Wind has to be blowing 15-17mph for them to generate properly. Also, there is not yet enough transmission infrastructure to bring all of the wind energy back to civilization. There aren't enough people that live around the wind farms to use all of the power is generated, therefore there was never transmission built to support that kind of generation capability. They're arguing over who is going to pay for it now - state of Texas, or the cities, or Obama, which brings it back down to the local level. Trickle up poverty.