One of the most frustrating expressions I came across in my college mathematics texts was "and, as would be obvious to the most casual observer..." I always thought to myself, "What? Obvious to you maybe."
Later, I became exposed to a new kind of analysis that also used the word "obvious" - the non-obviousness test for patentability under 35 U.S.C. Sec. 103. This test seemed simple enough: Would a claimed invention have been obvious at the time it was made to a person of ordinary skill in the art? Since it was an objective analysis based on the differences between the prior art and the claimed invention, it seemed eminently more rationale than "obvious to the most casual observer" test. But, of course, its application was far from simple.