I spend what I think is a very substantial part of my life thinking. Not the usual kinds of thinking, like what am I having for dinner, how much money is left in my checking account, or whether the people I work with like and respect me. Don't get me wrong: I do spend time thinking about those things. But I seem to spend a lot more time thinking about some different kinds of things. Like how to write a checkers program that can beat master level players. Like whether podcasting is actually effecting a change in the nature of communication in society. Like whether I could create a PVR that was simple to install and use on my Linux box. Or even whether I can create an Enigma machine simulator on an Atari 2600.
These things are pretty eclectic, but I really can't imagine my life without these kinds of thoughts. I think the biggest problem would be that without these (admittedly obscure) topics to keep my mind busy, I'd simply be bored. Bored out of my mind. It's not that any of these things are really important, they are just colorful billboards along the at times boring straight patches of the highway that is human life. I suspect that we owe much of the Web and the open source movement to feelings of boredom.
A more erudite exposition can be found here:
The Long Tail: The Awesome Power of Spare Cycles