Cisco 1000v
Chris,
Interesting post.
Here's a slightly different twist - the Cisco 1000v virtual switch has an equivalent control plane in an external Virtual Supervisor Module (VSM), which, according to Cisco .... "... This standalone, external, physical or virtual appliance is responsible for the configuration, management, monitoring, and diagnostics of the overall Cisco Nexus 1000V Series system"...
The 1000v is not a VM per se but a virtual Ethernet switch on a server - however, its control plane is on a separate/standalone (and external) VSM - a slight variation on your point.
Thanks,
Sridhar