[superuser2]

There is no point in using Docker if you're going to think about it in the way you're thinking about it, as just another way of subdividing boxes.

What we're excited about is using it as a building block in an internal PaaS so that individual application teams have a Heroku-like interface for deployment. Hosts are cattle (and managed by a traditional CM tool), containers are immutable and do not even have shells installed, etc. We don't have mature tools for orchestration, scheduling, networking, service discovery, etc. yet but this approach is what all the hype is about and much of the software popping up to fill that niche, i.e. Mesosphere and Kubernetes, is really interesting.

Machines having roles, engineer SSH keys being on machines, containers being logged into, etc. - in attacking these things you are attacking a strawman.