I think one of the major advantages of cloud services is that of resilience. I know there have been some very high profile cloud service outages in the past, but by and large there's a lot of redundancy built in to such solutions that most companies just couldn't even contemplate if buying the hardware and hosting themselves.

What I don't like is not knowing the underlying architecture my services are running off and having control over that. I'm sure you can always buy more resources, and even have burst packages which means you get more clout on your servers at busy periods which is very flexible. But when it comes to an issue of contention with other competing services and available resources are getting a bit thin on the ground - who has top trumps?