Shortly after I graduated from undergrad, my mom once asked me why I liked computer science so much. I told her that writing a piece of software is as near to the act of pure creation as you can get: you start with nothing but an idea, but you end up with something tangible. Or well, at least something to show for your work, if not something "tangible" per se.
Later in my career I refined that answer a little. I realized that for me, there's more to the joy of programming that the simple purity of writing lines of code. I like to do new things, but I'm impatient. I like to stand on the shoulders of giants, making connections between grand ideas that others have come up with.
If I were a pioneer in colonial America, I wouldn't be one of the folks beating the earth into submission with nothing but sweat and a plowshare. I'm not the kind of person who goes out to blaze new trails and explore uncharted territories. Those kinds of pioneers get the thrill of doing something new, but usually the only scenery they get to see is the scenery they're personally exploring.
Instead, I'd be an enabler: the general store-keeper. All those pioneers out there making history have to get their supplies from somewhere, and when they do, I'd get to hear their stories. I'd get to see their homesteads, and pass along advice and lore among visitors to my store. I probably wouldn't get to make history on my own, but I'd get to be a small part of a lot of great histories.
That's why I love my current job. Google has a lot of developer tools, like GWT, Gears, and Android, and a lot of pioneers are out there on the web doing cool new things with them. I'm not out there building the sites; instead, I'm tending my shop, getting them the tools they need, spreading their lore, and being a small part of a lot of great sites. Sometimes I even devise a new tool of my own, to help them out.
I'm excited by constantly being exposed to neat new ideas, and I love learning. I can't imagine a job more fun than where I am now, sitting in the middle of this crazy, furious, flurry of new ideas that is the open web and mobile.