Found via Warren Ellis -- it's from M. John Harrison's blog:
"Every moment of a science fiction story must represent the triumph of writing over worldbuilding.
"Worldbuilding is dull. Worldbuilding literalises the urge to invent. Worldbuilding gives an unneccessary permission for acts of writing (indeed, for acts of reading). Worldbuilding numbs the reader’s ability to fulfil their part of the bargain, because it believes that it has to do everything around here if anything is going to get done.
"Above all, worldbuilding is not technically neccessary. It is the great clomping foot of nerdism. It is the attempt to exhaustively survey a place that isn’t there. A good writer would never try to do that, even with a place that is there. It isn’t possible, & if it was the results wouldn’t be readable: they would constitute not a book but the biggest library ever built, a hallowed place of dedication & lifelong study. This gives us a clue to the psychological type of the worldbuilder & the worldbuilder’s victim, & makes us very afraid."