What will be interesting to see is how IT leverages few of the basic tenants of cloud namely – scalability & utility (if you leave security out of the discussion for the moment). In absence of a multi-tenant environment, the subject of provisioning the “right capacity” to address the elastic demand by certain applications will be a challenge. There might be a tendency to oversize even in private cloud environment. Also there will be applications that will require redesign/recode to adapt to a cloud model.

In public cloud, an enterprise can leverage the capacity of a cloud provider to address the elastic demand. The hardware is already there and you can just provision on demand. The cloud provider recovers his investment by multi-tenancy.

In private cloud, the excess capacity still needs to be provisioned by the enterprise IT. In case there are applications whose resource requirements are not conflicting and have different time based demand elasticity, there will be opportunities to leverage the underlying resources in the cloud.

I agree that we need more ‘ecosystem services,’ but would suggest they’re coming on-stream as every IaaS and PaaS provider worth their salt scrambles to fill the space. In a recent conversation with Michael Crandell (http://cloudofdata.com/2009/03/rightscale-ceo-sees-little-need-to-move-up-the-stack/) we touched on this a bit.

Compliance is definitely a tricky one, although a recent conversation with Salesforce’s Adam Gross (should be out in the next day or two) suggests they weren’t as concerned as I thought they’d be…

I agree with your sentiment about trust in public cloud, but I don’t think it will be as rapid as you think (wanna bet?). I think we need to see more ecosystem services that improve monitoring and management (think Rightscale), more providers with solutions targeting specific markets (think health care), perhaps even changes in regulatory and compliance requirements (a tough one), and fewer failures that send enterprises scurrying to their private clouds (think Carbonite).

I’m sticking with my opinion that enterprises will spend more money with private clouds than public clouds for at least three years. But we are both on basically the same wavelength here.

In a number of conversations in recent weeks, I’m seeing a lot of agreement that Private Clouds will be big… but probably only for the next 18-24 months. By that time, Cloud Computing vendors in the public Cloud will have managed to persuasively demonstrate that *most* people’s data is perfectly safe in the Cloud for *most* purposes, *most* of the time. There will be exceptions, obviously, and for those there may be a niche Private Cloud market in the longer term.