I hate to encounter code which makes me say, "I am looking at this statement and I do not know what it does." Even worse when "I cannot know for certain what it does." Even even worse when "this statement might be executed a thousand times and do a different thing each time." Because I know that the problem that costs time and money is not, trying to figure out what the code is supposed to be doing, but, figuring out what the hell it just did and why.