So I know a lot of people do Facebook, Twitter etc but for those of us that work doing any form of content creation of value desktops beat out most of the competition. For example... I am writing a white paper at the minute and doing so on a desktop. With a decent amount of grunt, good keyboard and dual monitors I can do stuff so much quicker than any other device, esp for media intensive ops.
There will always be a place for desktops.