Linux on the desktop--indeed, anything on the desktop--may soon be a very moot point... I got from point A to point B with a leap of intuitive thinking, which I will step through here. One thing I should note: when I use desktop in this conversation, I am referring to the home PC platform.As more and more home users are buying computers, they take them home, unwrap all the Styrofoam and bubble-wrap, plug them into the power and the phone jacks, and use all that processing power to (a) better mankind, (b) better themselves, or (c) download video clips of Janet Jackson. In a world where people take things more seriously, it might be option (a) or (b), but it is more likely that it will be something along the lines of option (c).
The home PC market really took off, in my opinion, when people wanted to get computers at home that matched the capabilities of computers they had at the office or their kids had at school. Parents wanted their kids to have access to the Internet for researching school work; kids wanted to play games. People wanted to finish that big report for the office at home; they ended up surfing eBay. That sort of thing.
PCs, which were meant to be tools of discovery and assistance, are also being used as entertainment devices. This is no big secret. What might be a big secret is the fact in the very near future, that's all a home PC might be used for in most of the homes that have them.