PaaS posses new questions about application support – as your IT environment becomes more distributed who is responsible for managing performance? IT Operations? Development? Your third party vendor? In a perfect world, The responsibility for PaaS (platform-as-a-service) cloud application performance must be the responsibility of the PaaS provider. SLAs are meaningless if cloud vendors do not work with the customers in a transparent manner.
Cloud-based infrastructure and software providers like Amazon and Salesforce are incorporating application development tools into their offerings, blurring the lines between IaaS, SaaS and PaaS
You can read more here: Platform-as-service offerings blurring lines between cloud packages