Clearly right now the market is approaching a two-horse race: Amazon AWS (expected winner) and Google GCE (biggest kid on the block). However, the public cloud reminds me a lot of the land-grab of social networking websites of the early 2000′s.
As with any industry, there is a land-grab rush. Unlike the social networking example, all of the sprinters here are established technology companies, some giants, that are either expanding service offerings, or entering a completely new vertical.
MySpace vs. Facebook