The key growth factor in object storage will be the cost of storing an object. With Castor being platform agnostic, it can run on any x86 ranging from an IBM blade server to a low-cost whitebox.
Scale-out is potentially cheaper than other alternatives, and should allow competition with S3.
The Dell deal and the Openstack initiative add credibility, and open the door to volume rollout.
I would add that I've been an OEM of Caringo, and like both the product and the team. If the pundit's market size productions come true, this will be a very competitive, fast-growth area, with Caringo playing the game well so far.