The people seem to be fed up with a bad economy, and Ben Ali's family making millions. The spark seems to have been the suicide of a jobless man who was arrested for trying to sell fruit and vegetables:

http://www.bbc.co.uk/news/world-africa-12157599

http://www.bbc.co.uk/news/world-africa-12120228

Tunisia's government has collapsed, partially due to food price inflation and unemployment, but also because of WikiLeaks.

One of the U.S. government cables released by WikiLeaks (via @spbaines) exposed the corruption of Tunisia's President's family, its reach into business in the country, and ability to transcend the rule of law. President Ben Ali's family was called "The Family" throughout the leak. The government attempted to block access to WikiLeaks earlier this month.

Here are some highlights from the June 2008 leak (read the full leak here):
http://wikileaks.ch/cable/2008/06/08TUNIS679.html