Wow! I didn't even realise that was a thing that could happen!
Like McDonals they have a really good idea of what to expect, in terms of trades each day, so they try to keep those coins online for that, and when traffic gets heavy flags start to wave to announce an unplanned buying pattern. Once those flags start to fly mgmt gets more coin so that they could take care of the new unexpected traffic.
As the ceo of coinbase explains, most of the coins are held off line, some locally, some not so local but in state, then more out of state by in country, then key parts for the remainder scattered around the world (perhaps 5 places). This way a major alarm doesn't have to sound if the need is only for coins stored offline locally.
see vid
http://www.youtube.com/watch?v=ZwG1roO70co&list=PLEUe0yAulQTtJp-KuUVxx_acD0B4cOh7o&index=11
