Michael Archer makes a case against portraiture in the Guardian recently:

Why does mention of portraiture make me snort with derision? For the sitter, to have one’s portrait painted is to indulge in a preposterous bit of self-aggrandisement, while to be a jobbing portrait painter is to exercise the lucrative employment of one’s skills in a manner that has nothing to do with contemporary art. To champion portrait painting is to hark back to a 19th-century view of what matters in art, just as to visit the National Portrait Gallery is to enter an archive of social history rather than an art gallery. But isn’t there something perverse about this view? […] portraiture, seems to be much less secure in its status. The act of commissioning a portrait is something few of us will do – it being restricted to those with more money than is good for them. There are more photographic images of individuals around than ever before – perhaps because of that, and the ease with which still more can be generated, the idea of producing a composed portrait strikes me as increasingly pointless. Even when we do encounter such a thing, we don’t always assume that what we’re looking at is a portrait. […] The figure in history is what matters. As with landscape, portraiture becomes pertinent when it breaks out of its straightjacket and offers something more than a tastefully composed and skilfully executed representation of someone. This is not to say that painting can’t matter in either landscape or portraiture, it’s just that it can no longer be a necessary and sufficient condition.

Portrait Art Has Never Been More Pointless (Guardian)