Disable/Enable collections on the fly?

[Jeff Mitchell]

Max--

Is there a way to on-the-fly enable or disable collections?  I'm 
thinking about this in the context of portable devices, where a user may 
not want to automatically mount/connect a device or may want to 
unmount/disconnect it at a given time.  If there were a way to 
enable/disable collections, then this would in effect be an appropriate 
way to determine whether to connect the portable player or not.

--Jeff