Try if possible to reuse existing modules, enhancing them is ok too.
(Laziness ?)

If you modify/enhance an existing module submit the patches to the author.
(hubris ?)

If you write a new module, (impatience ?) submit it to peer review polish it and then make it publicly available...

This way you'll get benefit of others experience, enhance things, avoid unnecessery 'pollution' of the modules list and get feedback about your code.

"Trying to be a SMART lamer" (thanx to Merlyn ;-)