A study of survey data collected in May 2009 was recently released.
The Natioinal Literacy Trust studied young people's attitudes and behaviour and the role of technology in writing. The study includes some data about boy writers.
"by exploring a greater variety of possible writing formats. For example, technology based formats, in the form of text messages, blogs or notes on a social networking site, feature strongly as a vehicle to encourage pupils to write more widely.
By showing that websites, emails, blogs and networking sites were among the most commonly written formats outside of school, this study highlights the importance of technology in informing young people’s writing choices."
Source: U.K. Literacy Trust: Writing Survey 2009 Page 35