According to a Wall Street Journal article, Pinterest has passed 20 million users, up from 1 million users in July 2011. As of now, however, the site currently has little to no revenue.
Link to Rakuten's press release:
http://global.rakuten.com/newsrelease/2012/0517.html
Link to the WSJ article:
http://online.wsj.com/article/SB10001424052702303448404577409212961081738.html