Linux.com have written an article about the departure of Matthew Garrett and the reasons behind his decision
Garrett did not hold any office in Debian, although he was a candidate for project leader in 2005. However, he has been consistently active in policy discussions and an active poster on the debian-devel and debian-legal mailing lists. In addition, he has been one of four members of Ubuntu's technical board, and doing work on laptop support for Ubuntu. He is described as “high-profile” by Benjamin Mako Hill, another active Debian maintainer. Steve McIntyre, who is currently acting as assistant to the Debian Leader says, “Most of the Debian Developers are sorry to see Matthew leave.” Some, like McIntyre himself, have blogged about it.