I think it would be a shame if SPCR started to become anti-fanless on principle. For certain classes of components it is relatively easy to run them fanless (cool hard drives such as Samsung Spinpoints, mobile/undervolted CPU's, etc). Power supplies are generally the hardest component to run without some kind of active cooling, but as you point out an essentially inaudible undervolted fan does the job admirably and at much the same dB level. But solid-state computing really is the holy grail of silent computing; it may be a couple of decades away, but there's no question that no moving parts = no noise.In fact, I've come to the point of view that it's mostly a disservice for SPCR to encourage fanless anything. If you are going fanless successfully w/o reliability issues, then it's because you really know what you're doing or because you haven't run it fanless long enough. (give it another year...) Fanless as a goal for most people (even in these forums) is not wise, it's not practical, it's not really "safe".
There is a certain performance envelope which it is impossible to exceed at the moment if you are going to run your rig fanless (or with only one inaudible fan in the whole setup); for instance I should think that running an X2 4600 totally passively is completely out of the question. However that kind of computing power is really overkill for a lot of computer users, and a 2GHz rig with moderate graphics capabilities should be well within the grasp of most determined SPCRers. I acknowledge that blindly promulgating fanless operation regardless of whether it will actually improve the subjective acoustic experience of end users is folly personified, but equally we shouldn't discourage people from going down the fanless route if it is a viable proposition for their requirements.