Interesting article in which a cloud provider did a slight pricing change, and one company racked up allot of bills from it. This reminds me of some of the stunts phone companies used to (and sometimes still do) with customers except replayed on the cloud. Moral of the story, have a backup incase you need to switch cloud providers fast.
http://www.theregister.co.uk/2013/02/15/heroku_marketing_misstep_draws_customer_anger/