These days when people call event handlers for their movieclips or buttons, they either do it at the clip level, or they do it in the root timeline, by prefixing their handlers with the instance name. The advantage with doing it the former way is that you are a all-in-one button that can be easily reused when you copy and paste the asset into another Flash document. The downside is you have to hunt around for your function if your mc clip is deeply embedded. The pros and cons of the latter way is pretty much just the opposite.

A nice idea would be to create an extension to allow the coder to use the former way (making all entities well-encapsulated) but allow them to be able to find their code easily by simply selecting a list of instance names, they can navigate to the handler code for that that instance.