BD just brought up something in another topic. We need this guideline, 'nuff said. Here's a first draft:
Don't use ranked maps to justify your map. The ranking system is not perfect; things that should have been picked up in the modding process are not always caught. Also, the ranking standards change frequently; what was allowed 3 months ago is not always allowed today. Therefore, ranked maps are not always a good indicator of what is rankable and should not be used to justify your map. If the best you can come up with is, "Another map did it!", you should probably rethink what you're doing.