The entire model looks to me like it never had even the most superficial security analysis done. It's like a smorgasbord of insecure decisions:

* the false sense of security from putting signatures in the manifests then ignoring them

* loading signing certs via the network with no provision for pinning

* happily loading untrusted/unsigned images by default (npm, rubygems, installtools, etc. also do this but why repeat their awful design mistake?)

* running basically everything as root (because why deal with all those messy permissions?)

My sysadmin Spidey-sense has been tingling at the rate of change in the Docker ecosystem since it went from "interesting POC" to "we think it's production ready" in a shockingly short period of time. Things like this sadly confirm that initial pessimistic view.