The collapse of newspapers seems to be overdetermined at this point: rise of new media, falling quality, ideological bias (in some instances). But I have a hypothessis that may seem somewhat far-fetched to add to the list: a lifestyle change in America, namely, the decline of eating breakfast at home.
This is only a hypothesis, because although I have looked around some, I haven't been able to find really good data on the frequency with which people eat breakfast at home. Casual empiricism, however, suggests that fewer people eat breakfast at home than in the past and are more likely to either it not at all, in the car, or at their desk.
I confess that this hypothesis is generated by my own behavior, but it hardly seems atypical. I do eat breakfast at home and I read the newspaper every morning as part of my morning routine. My parents (now retired) do as well. Since I outgrew reading cereal boxes a few years ago, there are few substitutes for the newspaper when I'm eating my daily breakfast. Certainly not a laptop.
A related factor is the elimination of afternoon newspaper delivery. I'm sure circulation was low for those as well, but this further reduces the available time for newspaper reading.
One factor does seem clear now: most Americans now consider the newspaper more of a luxury than a necessity and so when household budgets are cut when the economy slows, the newspaper be one of the first things to go. Movie listings, game times, etc., all used to be found in the newspaper, but those are things that are found on-line now.
Anyway, I've never seen anyone test the hypothesis of whether this lifestyle change has accelereated the decline of newspapers. Younger cohorts both eat breakfast less frequently and are more likely to have to rush to eat breakfast. But for me at least it is really only my morning routine (which I can afford because I'm a professor so I don't have to race to the office every morning) that keeps me reading newspapers at all.
Sorry, I inadvertently left Comments closed on this if anyone wants to make fun of my hypothesis, or in the unlikely event anyone thinks that it has any value at all. Although Orin's post seems to be the more productive place for comments now.