I think we must ensure to do not leak any styles from each module as @gordonbrander  says, using the chain `.bb-headers .action` makes `.action` a generic name, being isoltaed under the `.bb-header` definition.

If there is some global `.action` inside an application is true that is going to collide, but that is as unavoidable as being affected for some generic `span` rule.
So we must take care on not leaking from our module instead of thinking what could affect us from other modules.

Using `.bb-` prefix for all clases will be ended in a mess of verbosity and will make difficult to differenciate main module clases (`.bb-header`, `.bb-list,` etc...) from internal components of a module (`.bb-list .action` VS `.bb-list .bb-action` VS `.bb-action` as module definition )

I believe that recommendations from other front-end experts are great in order to pick ideas and guidelines, but we must define our own set of rules based on our needs.