Amazon Web Service’s announcement yesterday about their AWS Elastic Bean stalk offering was a significant step in their inexorable movement up the stack from IaaS towards PaaS (platform as a service), offering a Java PaaS based upon a Apache/Tomcat/Linux stack.

At the same time, the SaaS players are moving in the opposite direction, as demonstrated by Sales’s recent acquisition of Heroku, the ruby PaaS provider.

Up until now, I’d have argued that PaaS has been the least mature of all the “aaS” siblings, with significant risk of lock-in, vendor failure risk etc, but this is rapidly changing and PaaS will become the main battleground between all the vendors as the SaaS players make their offerings more and more configurable/flexible and the IaaS vendors try and simplify their typically quite techy offerings for a wider audience.

There’s good further material of this topic on Krishnan Subramanian’s blog.