The vendor mafia's Linux vendetta
Just about every device on my machine is running on a driver written by the community. My video driver, my disk driver, my sound driver ... the list goes on and on.
For all the arguments against Microsoft and its anti-competitive practices, the one thing that really holds Linux back is the complete, embarrassing and possibly negligent support for it by vendors. Microsoft really has nothing to do with it.
Windows rules the desktop because my mother can walk into Incredible Connection and buy any device in the shop, take it home, pop in the driver disk, and it will work. For Linux, there may or may not be a community-written driver for whatever software I want to install.