Yesterday several members of Joyent’s team attended Structure ’08. Jason Hoffman was on a panel that produced some interesting debate about whether clouds should aim to be open. The story was even picked up by the Wall Street Journal’s Don Clark in an article entitled Finding A Friendly Cloud
Jason Hoffman, founder and chief technology officer of a cloud-computing specialist called Joyent, was particularly pointed in warning that Google’s App Engine could represent a lock-in to developers. It is possible to build “a loving cloud,” he argued, that would make it easier to create applications that could be easily moved among different services. Other panelists kept calling Google’s App Engine “proprietary,” which to many techies is equivalent to labeling it both evil and outdated at the same time.
Here’s video of the exchange Jason had with Google’s Christophe Bisciglia
Jason A. Hoffman 
One response to “A Loving Cloud”
Totally agree.
There are three levels of “cloudiness” with the best example in each.
– application: Salesforce.
– platform: GoogleApps.
– OS: Amazon’s EC.
I would say they are all “open” to varying degrees (documented APIs, data accessibility, etc…), but as you so commnetd so accurately in the panel, there’s a “weak” lock-in for all but true clouds that comes inherently with a vendor providing a more time-to-market environment.
The key question is how much flexibility do you want/need for your project? As you drill down the axis above, you trade off more flexibility for increasing complexity.
All-in-all, I’d say lock-in will become more of a hindrance to vendors like Salesforce or Google, as more “flexible” clouds come online.