Disclosure: I've been working with Tutum since the initial team.

Tutum was actually a container hosting service at first but we found there were a ton of technical challenges in multi-tenancy with hundreds/thousands of containers and it's hard to build a level of trust that larger IaaS providers have like AWS.

Hosting puts you in direct competition with IaaS providers, while being a middle-man can provide more value-add and you get to work with the other providers to strengthen your solution.

The multenancy challenge comes from the lack of isolation in container. Therefore, people nest containers in VM and put a scheduler atop.

But if there is secured, isolated container, we won't need the VM nor the scheduler, the container becomes the hosting platform, aka EC2, DO.