There are two things I'd like to add:

The first is that it really does feel more like context switching. I don't know if I was born with it or taught it by the Internet, but the cost of context switching seems very small to me. Going from mail to movie to code to web is all very quick. And sometimes I can even throw in tracking the laundry and making dinner too.

The second is that sometimes it feels like there are different parts of the brain that need different forms of stimulation. For example, I have to be fidgiting or otherwise doing something when I talk to people. I like having a Rubick's Cube near the phone which I can solve over and over, or a pen I can disassemble and reassemble. It's like physical white noise. Add that to auditory white noise and I get my best thinking environment. If I can keep those parts of my brain busy, the higher order parts don't get distracted as easily.