For me, being tied to Amazon's cloud is a deal-breaker -- I realize you can choose to run your own (and with linux, docker, chef, etc. that's not an insurmountable challenge) and probably would choose to run my own -- but being locked in otherwise I don't feel good about, especially when I don't think AWS is particularly great, or particularly innexpensive. I think Azure has the better offering of any of the cloud providers, TBH (though, disclosure, I work for Microsoft and near enough to Azure to know some people over there) especially when you consider the greater number and geographic spread of data-center regions, but still, I don't want to be contractually obligated to forego other cloud providers that I might think provide the best value for my needs.
Furthermore, I can't think that cloud-hosting revenues alone on their end would make this a worthwhile venture. They've got to be going after micro-transactions (or perhaps its already included in their definition of cloud services) IMO -- and you pretty much can't roll your own payment processing solution without a whole lot of work and without taking on a lot of security considerations and all the risk that entails.