It's possible, but not trivial. Especially when the developer is using 100% event delegation, you have to run that node against all the potential selectors of parent elements...
.live() .delegate() and (usually) .on() will leave the handler on a parent node, making sniffing out all active handlers an expensive DOM-walking task.
Given this limitation, the only problem with displaying event handlers is that developers who don't understand the underlying event model of the platform might not grasp the correspondence between the high-level abstractions in their library-using code and the low level DOM behaviour. Clearly any such developers will become more effective once they know a little more about the platform they are working on.