Micah, you have described what online marketing researchers have coined "telewebbing." The act of watching television while surfing the web.
Studies show that when people use their computers and watch TV, the TV -- an inherently passive medium -- fades into the background.
Most of the research is old -- dating back to 2000 -- but here's a good article from 2002 on the topic.

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Not quite, methinks
Last night, I sprawled on the sofa in my living room with my laptop on, reading email and blogs, while watching TV and chatting with my wife intermittently about the pictures of the tsunami we were seeing as well as other random things. Was I watching TV, surfing the web or spending face-to-face time with family?
The Institute for the Quantitative Study of Society has a problem. Its study tool doesn't allow respondents to choose "multi-tasking" as an option in their self-reporting.
So, while the drop in TV watching is not surprising (and certainly rings true to my own experience), I'd like more textured observation of people's Internet use before I accepted IQSS's claim that it reduces family face-to-face socializing by such a large degree.