A true story from South Africa. 

Connectivity is not good within the country, although data links from outside are receiving investment.

So a corporation with sites 50 miles apart needs to send about 3-4 GB of data between them once per day. Cost prohibits a dedicated line between the offices, so the internet is an obvious answer. Remarkably this is taking 6 hours due to the poor bandwith across the internet.

So they have trained up some carrier pigeons carring encrypted memory sticks. The first few flights have take 3-4 hours, so presumably the pigeon stopped for lunch, but with a little training they able to do it in a couple of hours.

So the barrier to Cloud computing may be the infrastructure which is outside your control.