Gartner says the Platform-as-a-Service (PaaS) market should be worth $1.2 billion this year, up from $900 million last year, and hit $1.5 billion next year on the way to $2.9 billion by 2016.

Its calculations include everything from Salesforce.com's Force.com to discrete application infrastructure components, such as databases, messaging and what it calls "other functional types of middleware offered as a cloud service."

Since the widgetry is less mature than IaaS or SaaS and more popular in mature economies - like the US which represents 42% of the market - Gartner says "PaaS is where the battle between vendors and products is set to intensify the most."

The researcher also figures fragmentation is slowing adopting. "Fragmentation will be impossible to deal with when users and service providers start to implement large-scale, business-critical applications requiring the simultaneous and in-concert use of multiple PaaS capabilities (for example, user experience, application servers, DBMSs, security and messaging)."

There are at least 150 vendors now - including Oracle, SAP, Microsoft, Salesforce and Red Hat with its open source OpenShift - so it seems to Gartner that "rapid aggregation" of PaaS components into suites is in the cards - as witness Oracle just taking a stake in Engine Yard and Salesforce buying Heroku.