...maybe I'm confused... Is your premise that they will only run their application/service internally?
Normally what I've seen is, develop on OSX and then push to Heroku (Linux) / <infrastructure provider of choice, running a Linux VM>. Why then wouldn't the natural progression be, develop in boot2docker and push to <docker PASS of preference>?
But almost always the module or service that you work on relies on other services and datastores. boot2docker can help you pull down an entire stack to your workstation and not rely on connecting to an external network. You can essentially work on Airplane mode.
Or, you can architect your module/service to run the things it depends on in a self-contained manner and avoid creating a hard dependency on virtualization of Linux.
Normally what I've seen is, develop on OSX and then push to Heroku (Linux) / <infrastructure provider of choice, running a Linux VM>. Why then wouldn't the natural progression be, develop in boot2docker and push to <docker PASS of preference>?