Not yet succinctly stated, Dave's Law of ProximateAcronyms is:
When we employ acronyms in writing, we trade off brevity against a reader's ability to expand the acronym. The same acronym can take on different meanings in different "domains of discourse". By employing mixed acronyms, flow suffers, and the likelihood of confusion increases. Readers are forced to stop and back up to ensure that they've chosen the correct expansion for an acronym.
Consider this example. Assume the context is "web development."
In context, ASP probably needs "Active Server Pages", and JSP means "Java Server Pages", but does DIY mean "Do It Yourself", or has some vendor just introduced a new web programming language or environment? ASP and JSP are drawn from a specific domain of discourse (web programming), and DIY is drawn from a different domain. Confusing? Perhaps. It was to me the first time I read it. I had to stop and back up to verify that I hadn't missed or misread something in the previous sentences, and was still left with a tiny seed of doubt that Microsoft had introduced yet another acronym that I hadn't run across yet.
-- DaveSmith
Have any favorite examples of proximate acronym misuse? List 'em here.