Of course, there are limits to sharing. For a while, the couple subdivided an office. Despite that difference of opinion, proximity is the reason they hammered out a job-share arrangement to begin with. And although the evidence is largely anecdotal, their numbers seem to be swelling. Of course, there's a price to pay for job sharing.
Money can be tight.
Securing tenure for both halves of the appointment is dicey. But on the whole, job-sharing is a welcome trend, among professors and administrators alike. If an institution can't do that, a shared position can be a good alternative. Twenty years ago, academic couples were a rarity. Now, administrators who are not creative on the job front risk losing out on both halves of a couple if the institution can't find work for the spouse or can't negotiate time off for a parent.