When I created my websites for Statistics 434 and Statistics 955, I naively and happily included as "rules" those things that I thought would lead to the best classroom experience for everybody. No eating. No cell phones, and no open laptops.
My reasoning was manifold --- or at least bi-fold.
First, even if a person with an open laptop is conscientious and only keeps notes, there are two levels of distraction. One source of distraction is to the students around the laptop user. This distraction is possibly tolerable if the laptop user really only takes notes 100% of the time. On the other hand, if the laptop user ever yields to the temptation to catch up on his mail or to play a little solitaire, then everyone in visual range will be substantially distracted.
Second, the laptops distract me. It is by no means easy to keep a lecture lively. You have to engage folks. Also, to keep from going nuts, you have to have the sense that people are following what you say. This sense is hard to get from a person buried behind a screen.
It turns out that there are professors "getting into trouble" for not allowing laptops. In the linked case, a law professor has students who are howling about not being able to use their laptops in lectures.
To be sure the whiners are at the University of Memphis Law School, which does not make many top-ten lists. I think that students at Penn, or Yale or Harvard would take a different cut.
They are more likely to see their time with their professors as a scarce commodity. This exposure is expected to serve them for a lifetime, yet it only lasts a few years. In such enviroments of priviledge, students and professors can be expected to coordinate their concerns.
If a professor is uncomfortable with open laptops (perhaps through some unfortuate dint of personal foible), then it seems to me that the collective choice should be clear: no laptops.
If that is not the collective choice, then it seems to me that collective offers the professor a sobering message. Specifically, the students are saying that the marginal value of the lectures is eclipsed by the marginal value of taking notes by computer versus taking notes by pen.
To my fellow professor I would say, if your marginal value is that thin, it is time to get out of Dodge. The issue is not laptops, but content.
In computer science and some parts of engineering, it has become common place for students to have open laptops in lectures. In statistics and mathematics, this is still reasonably rare. Part of the issue is that mathematical notation is much more easily put down with a pen than by typing.
The culture of laptops is evolving, and there may well come a day when every lecturer must face a sea of open laptop backs and ghostly faces illumiated by the glare of computer screens. This seems sad, but it is far from society's greatest challenge. Most folks will simply go with the flow. That would be my plan.
Maybe we will get lucky and the laptop experience will drive us all back into the world where classes of eight or ten are the norm and where students do as much talking as professors.
It worked for Plato; it could work for us.