Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
In 2007, thanks to netbooks and Vista, Linux briefly exploded onto the desktop. Microsoft soon realized they were losing the low-end laptop market and they brought XP back from the dead and practically gave it away to original equipment manufacturers (OEM)s. It worked. Linux's popularity receded. In 2012, Microsoft is once more bringing out a dog of a desktop operating system, Windows 8, so desktop Linux will once more get a chance to shine... if it can.
Linux is more than good enough on the desktop. Just ask Google, which used its own Ubuntu-spin, Goobuntu, not just for its engineering desktops but for everyone's PCs.
While much of the reason why Linux hasn't gone much of anywhere on the desktop has been because of Microsoft's iron-grip on OEMs.