From CBC Nova Scotia:

There's a good reason wind turbines don't usually collapse.

Turbines, like the one that failed catastrophically in Cape Breton last week, get regular inspections and maintenance to keep them at peak performance.

Any issue with mechanical efficiency — or worse, downtime — results in a loss of profit.

The 20-storey-tall Enercon E-82 turbine that now lies bent over in a wooded area of Nova Scotia was inspected every three to six months by workers with the company. 

...Enercon officials emphasize the collapse happened during a scheduled component exchange, not during construction, installation or regular operations.

While workers were replacing the component, an incident occurred, the company said. The workers quickly evacuated the site before the turbine's tower buckled and sent the blades plummeting to the ground.

Some residents of Port Hawkesbury say they saw the turbine spinning unusually quickly before it fell.

The Canadian Wind Energy Association says this collapse was the first catastrophic failure of its kind in Canada.

For more see Cape Breton wind turbine was regularly inspected before collapse