Whats the interaction between systems based on Mesos, which can (and many do) use containers? Is this really designed for more multi-tenancy with lower trust over same-org clouds?
Docker solves the problem of running things in a repeatable and infrastructure-agnostic way. Mesos solves the problem of telling many nodes what to run and when.
In other words, Docker + Mesos is a killer combo. There is already experimentation underway to use Docker as an execution engine for Mesos.