Google App Engine and the Gathering of Clouds

How many Cloud Computing platforms would you say there are today? 

Some abhor the notion of there being multiple clouds – by this thinking there is only one “cloud” in an almost Zen manner, meaning “the grid” and the ability to reach in, somewhere somehow, and use someone else’s compute capacity, web apps, services, storage, etc.  Some others, however, as Amazon and others roll out their branded ability to do that reach, are beginning to call these “clouds” — I prefer to think about them as distinct platforms enabling cloud computing, but that’s starting to become a hazy definition. 

Next week the world will hear more about Microsoft’s Mesh strategy.

I feel like an observer out on a prairie on a hot summer afternoon, watching the sky as cumulo-nimbus shapes emerge and burgeon across the horizon.  The multiplicity is going to inevitably lead to feature differentiation, competitive marketing, a full hype cycle with naysayers and boosters (see Fortune magazine), down-market competition, shoddy wannabe clouds, boom and bust, market shake-out, etc. etc. – good times! 

How many such platforms (how many clouds) will there be in future?  How many should there be?  And if multiplication really occurs, is this any different from “utility computing” and aren’t we heading back to the days of the mainframe-model of time-sharing?