Richard Poynder has published "The Open Access Interviews: Sir Timothy Gowers, Mathematician " in Open and Shut?.
Here's an excerpt:
The idea of arXiv overlay journals was in the air for a long time. I think one impulse behind Discrete Analysis was the very hostile reaction from many people to the setting up of the open access journal Forum of Mathematics by Cambridge University Press, which (after a three-year free period) charges £750 per article.
It seems that a large proportion of mathematicians are implacably opposed to article processing charges, no matter what assurances are given that authors themselves will never be expected to pay out of their own pocket, and that ability to pay will not affect the choice of which articles to publish.