When I talk to each person about these behaviors, there’s not a lot of conscious decision-making going on here. The web-page-highlighters aren’t intending anything when they do this, it’s just something they enjoy doing. But even though these behaviors don’t help move any tasks or goals along, they’re satisfying. And because they provide a release for nervous energy and/or let us be expressive, they become an extension of ourselves to which we have some small emotional connection.
It was interesting to run across this post—an examination of the widespread, purely emotional attachment users have to the “bounce” feature of iPhone scroll views—just as I enter the final stages of an iPhone project where my designer Neven and I had considered putting the bounce reflex to an actual productive use. We may still revisit that interaction at some point, but I think this article makes an interesting argument in favor of just keeping that gesture a “free” (that is, purposeless) interaction.