The first three Graham factors, the “primary” ones, are of no probative value concerning the issue of whether a claimed invention would have been obvious. They present a series of meaningless hoops to jump through for courts, parties, and juries, to the extent juries address the issue.
The Graham factors are: “ the scope and content of the prior art,  the differences between the prior art and the claims at issue,  the level of ordinary skill in the pertinent art, and  secondary considerations, otherwise known as objective indicia of nonobviousness.” Ecolab, Inc. v. FMC Corp., 569 F.3d 1335, 1349 (Fed. Cir. 2009). The first and third of these factors are decidedly neutral, since discoveries in crowded, highly skilled fields can be just as obvious or non-obvious as discoveries in sparse, low skilled fields. The level of ordinary skill in the pertinent art is inherent equivocal. A high level of skill suggests, on the one hand, that any invention should be deemed more obvious because these highly skilled folks would have been able to combine prior art references but at the same time suggests that if an invention was obvious then it should have been invented earlier by one of these highly skilled folks in the field. Concerning the scope and content of the prior art, the definition of the field of an invention is itself precarious, since an invention is necessarily new and may well span more than one “field.” Moreover, the scope and content of the prior art is subsumed into the second factor. So those two factors are meaningless. [Update: See CELSIS IN VITRO, INC. V. CELLZDIRECT, INC. in which the majority (split opinion of course) notes that the crowded field, in this case, favored a finding of nonobviousness: "As to the scope and content of the prior art, the district court correctly emphasized and found based on the preliminary record that the art was a crowded field for many years and yet there was not one reference to [an aspect of the invention at issue]."]
The second factor (differences between the invention and the prior art) seems at first blush like the key Graham factor, but it does nothing but restate the statutory definition of obviousness, which simply states that an invention is obvious if the differences between it and the prior art would have been obvious. Helpful. Indeed, this factor is neutral as well. Sometimes a small change from the prior art can result in a major breakthrough, and sometimes it can be just an incremental, obvious step taken in the ordinary course of technological development. In the case of the electric light bulb, for example, the difference between the design that was commercially viable and the prior art was very small. Thus, the three main Graham factors have little bearing on the ultimate question, which is presumably whether an invention would have been a no brainer and should not result in a term of monopoly for the person who first filed an application for a novel combination.
The last Graham factor, secondary considerations, is the only Graham factor that has any meaningful relevance for determining whether an invention was a good one. In practice, however, these are often given short shrift by the Federal Circuit and the PTO. These considerations, such as long-felt need, industry acceptance, failure of others, copying and unexpected results, all provide at least some evidence that the invention added something useful to the existing state of knowledge.
As a whole, the Graham analysis never directly seeks to determine whether the invention was the result of a good idea. Only after somehow concluding that an invention would have been “obvious” based on the first three [non-]factors does a court even turn to the most pertinent available objective evidence for that issue.
The bottom line is this: Obviousness is completely unpredictable and has been for many years. The determination is in the end at the whim of whatever three judge panel of the Federal Circuit is drawn. The test used for this “question of law” has no analytical rigor. Stripped of the façade of its boilerplate factors, it boils down to the opinion of the court. That makes obviousness both unpredictable and fundamentally unfair. It is time to toss Graham out. And until the courts can devise a legal framework that produces both fair and predictable results, obviousness should be left to juries to decide.