Why is there more public PaaS than private PaaS?

I asked on Twitter: “For IaaS there’s a fair mix of public and private. But PaaS seems very titled towards public right now. Any idea why?”

Here are the responses I collected:

@wrecks47 challenged the proposition:

• I see the opposite. I observe much more activity in private PaaS rather than public PaaS.

Others seemed to agree and offered these explanations:

@reillyusa and @mfratto think it’s because it’s too hard to build a private PaaS:

• Complex and not too many understandable reference architectures – personified by why Azure appliance is taking so long to appear.
• much harder to build a PaaS in house?

@ryanprociuk and @garnaat think PaaS are very specific (though it’s not clear to me how that explains its lacks of private deployment):

• PaaS may not be as generic as IaaS, specific to a technical solution. IMO
• I think a private PaaS might be very domain-specific. Current PaaS target a narrow range of scale which can be generic.

@somic thinks that in a private setting (presumably without specialized app services) there isn’t much to gain by offering PaaS versus letting people run a container on top of IaaS (though this begs the question why don’t private PaaS provide these services like public PaaS do):

• imho today’s paas, in a private deployment, is just a webapp container – not revolutionary enough to justify a move

@robcheng thinks it’s mostly politics:

• the same agendas that cause companies to embrace private cloud make them suspicious of PaaS (whose jobs/teams become obsolete?)

@cloud_borat‘s interpretation is just that middleware marketers aren’t as savvy as their infrastructure counterparts.

• our expert analyst Igor say that because app server marketing people suck more and not label appserver as private PaaS

Thanks all!

[UPDATED 2011/7/5: This was originally a Google+ post, but it really belongs as a blog post here so I am glad this is where you are reading it. The next post explains why.]