This is a bit old by now, but this tweet from the Write the Docs conference in Portland has been open in my browser for two months:

"Bad documentation is a bug." #writethedocs

— Siobhan McKeown (@SiobhanPMcKeown) April 8, 2013

The quote appears to come from Jennifer Hodgdon‘s talk on how to motivate developers to improve their API docs. Andrew Spittle’s write-up of the talk can be found here.