Mariela Castro Twitter debut sparks Cuba dissident spat

The daughter of Cuban President Raul Castro has made her debut on Twitter, only to be confronted by a dissident demanding free speech. The full article is here <http://www.bbc.co.uk/news/world-latin-america-15649113>, and shows how micro-blogging can be used for free speech, or does it? In a country where only about 3% of the population have access to the Internet, can it really make that much of a difference?