The best arguments so far, as far as I am concerned, come from Semilog and Matthew:
For most of the history of photography, the problem faced by most photographers most of the time was how to get enough DoF — not how to minimize it. The dreamy, creamy, overly romantic, shallow DoF look was at one time the norm and it was precisely this norm that a group of photographers on the American west coast rejected when, in 1932, they founded Group f/64. (Semilog)
Though I'd add that it wasn't just shallow d-o-f: it was also deliberate softness, muddy tonality and 'control' processes such as bromoil, a.k.a. 'muck spreading'.
I propose that it's not a fad, and will become (remain?) a permanent and significant part of the visual language of hobbyist photography. . . Creating shallow depth of field has gone from a side effect of needing to photograph in low light to an accomplishment available only to those who have purchased different equipment. As such it's a goal to be pursued for its own sake – an irresistible temptation for a small but prominent sub-set of our hobby. . . (Matthew)
The last sentence is a bit cynical but, I think, accurate.
And of course as Dotur points out,
I might be mistaken, but the nauseating effect of the clear objects rendered in very poor focus in broad daylight can be partly caused by the increased contrast and saturation of modern lenses - not to mention the deadly post-processing sins. Higher contrast and saturation create unpleasant and distracting effects. Intensive color blots within the blurred background/foreground act as unnatural artifacts - they scream, they are too strong and thus draw attention away from the intended shallow focus, ruining the composition.
The numerous selective focus shots from LF/MF era are usually black and white or monochrome - the lenses were softer and the shutters were too slow to allow the outdoor use of wide-open lenses.
Thanks to all, but to those three particularly. The entire thread has clarified my own thinking on the subject, and it is clearly of interest to others too.
An interesting parallel is with 'frozen motion' shots when 1/1000 second shutter speeds became widely available: I think I recall that these became popular for a while. What is curious is that they are much less common now, even though we have 1/2000 and faster speeds to play with. This argues first, that 'because they can' is not necessarily a compelling argument, and second, that 'frozen motion' shots are probably even more difficult to do well than shallow d-o-f shots in good light.
As for jj who appears to think that I am against all forms off shallow d-o-f in good light, and that I am peculiarly irritated by shallow d-o-f, no, that's not the case: there is a difference between robustness of phraseology, and hyperbole. Like Pablito. I think that to a considerable extent, it is a fad and will decline, but like many others, I do not believe that it will go away completely: it will remain a useful technique, long after it has ceased to be over-used.
Cheers,
R.