Getting even simple things done with a slightly underpowered computer and a bunch of web-based applications means you spend a lot of time waiting. Waiting for TypePad to publish a post, waiting for Gmail to populate the screen with a list of the latest messages, waiting for an image to download so you can start editing it in Photoshop, waiting for Photoshop to launch.
Each of these delays is tiny, maybe on the order of five to twenty seconds, or a minute at the most: Delays which, taken individually, are negligible. But over the course of a day, they accumulate, not literally but psychologically, so you start thinking: What else can I do while I wait for this Ajax-ified web page to load? So you flip to another tab, or jump over to your email program, or respond to someone’s IM.
The result: A five-minute task (writing and publishing a blog post, for instance) gets spread out over half an hour, interleaved with a bunch of other micro tasks, because that five minute task contains half a dozen annoying little delays that you’d rather avoid.
Your computer has trained you to become a task-switcher. It has trained you to spread your attention out across multiple tasks simultaneously, devoting only a little time to each one in turn.
This is a major design flaw in all modern computers, because the computers are designed to provide beautiful, translucent, animated interfaces, not to respond instantaneously to human commands. And, I’m afraid, Web 2.0 style applications are only making it worse.