Benefits

In my view, the main benefit of Decisions-as-a-Service is that it levels the playing field between large and smaller players in terms of ability to implement sophisticated business logic.  No longer is it necessary to shell out millions of dollars in capital expenses to get access to a decent decisioning platform.  Instead, users can start designing and implementing automated decisioning through subscription or per-click models, essentially providing instant ROI.

A number of features are critical to make this model work:

• Shallow learning-curve business logic design interface.  The creation and deployment of decision flows needs to be intuitive and easy to learn, so that the users can truly be business analysts, instead of IT personnel. 
• Superior data connectivity.  Distributed data is essentially inherent in the hosted services model.  The platform must be able to access data easily wherever it is, given appropriate credentials.
• Superior system connectivity.  Decision platform do not just interface with data sources.  In many cases decisions need to be delivered to live systems that are likely to be remote.
• Shared resources.  While sharing of resources is not absolutely required, it does help to keep costs down.  This is important if small to medium-sized entities are to be able to afford access.

There are likely others, if you can think of them, please let me know.