Personally, I don't think duplicated modules are that big of a problem and it is certainly something we should _not_ punish people for. I'm a firm believer of the fact that "deliberate duplication" is a good. "Unfortunate duplication", i.e. duplication as the result of the fact that the author didn't know an almost identical module already existed, is something we have to reduce though.
I have a pretty good idea of existing modules as they stand now, not all, but a fair proportion, and would be interested in helping with this. When I read the first e-mail in this thread I immediately thought of a "duplicated module hall of shame" (possibly with a nicer title) wiki in the contributed module status group or similar, to serve as a reference point for people to avoid yet another duplicate. I can think of at least 3 candidate sets of module for this already.
-- Dries Buytaert :: http://www.buytaert.net/