(slaps head) The irony is that I wrote something similar to that for Winforms. For my base classes for textbox, combobox, etc., I set up a few custom properties so that all I have to do is set one or three properties on the prop sheet for each control (depending on which control it is) where I need to set up binding.
So I haven't had to write any code for 'bindings.add(), displaymember = 'whatever', valuemember = 'whatever', in a long time.
I don't do much Web Form development, so it didn't occur to me until I read your solution that you could take the same general approach. Great answer!
Kevin