Bit.ly received 2.1 billion clicks on its links in November 2009

"“People shorten the URL, send it to their wife and say, ‘Hey honey, look at this product’,” said John Borthwick, chief executive of Betaworks Studio, which runs bit.ly, the world’s most popular address shortening website.
“Somewhere in the region of 10 per cent of the bit.ly links get an extraordinary number of clicks. Links to big stories, such as Tiger Woods stories get millions of clicks.”
Bit.ly received 2.1 billion clicks on to links created by its shortening service last month."
Source: The Times, 7th December 2009