Laptops in the classroom: tool or time-waster?

The semester will shortly begin at universities around the country, and with it the latest chapter of every professor's dilemma about students' use of laptops in class. For those unaware of this issue, many professors believe that laptops (and now mobile devices connecting to the Internet) threaten to bring an end to higher education.

Students find it convenient to take notes in class on these devices, but over the years more and more students have started to use laptops for various Internet-related activities — and paying less attention to the class.

Professors now need to figure out which policies to adopt regarding the acceptability of laptops in class. Five years ago nobody thought much of it, but now it’s become a common topic for discussion (or gossip) among faculty. (Some universities have adopted schoolwide policies. I have been told, though I have not confirmed this, that Harvard Business School bans laptops and has turned off wireless connections in classrooms. I also heard an unconfirmed story that the Kennedy School Student Government had considered requesting that laptops/mobile devices be banned, but in the end didn't do so.)
 
Though the question is a modern one, it raises ancient philosophical issues. The most basic one is whether banning laptops in the classroom (and/or banning their use for Internet surfing of various sorts) is paternalistic and hence unjustified. If students want to sacrifice part of the value of their expensive classroom time by multitasking, do faculty members have any right to stop them?  One might even argue that competition from the Internet is good, like other forms of competition, because it keeps faculty on their toes — bore the students, and they are off to the Internet.
 
These are not stupid arguments. But I have two counters.
 
One is that — especially at a place such as the Kennedy School, where we are educating people to serve others — student failure to pay sufficient attention in the classroom is likely to hurt their ability to do the best possible job after they graduate in serving society. Multitasking is unlikely to cause a student to do so badly in a class that he or she fails to graduate from the Kennedy School (if it threatens to do so, it is likely to be self-limiting), and probably won't affect a student's grades enough to cost the student a desired job. But it is likely to worsen the ability of our graduates to perform at the highest possible level on their jobs. Since education in other programs also is likely generally to produce gains for society, poorer student preparation hurts society, not just the student who is multitasking.
 
There is also an issue of respecting others in the classroom. Students who multitask on the Internet are not just showing disrespect for their teachers, they are also showing it for their classmates, suggesting that what people are saying doesn't merit undivided attention. This disrespect hurts others, not just the student who is multitasking.
 
By the way, I am curious whether this is an issue in countries outside the U.S., and, if so, how it is handled.
 
FYI, my own class policy is announced in my syllabus, as follows (emphases in the original): "In class, use of laptops to take notes is fine. However, use of laptops in class to check e-mail, surf the Web, use Facebook or Twitter, text,  etc. [is] unprofessional and disrespectful to everyone in the classroom. All mobile devices must be switched off during class." (With the spread of iPhones, I am adding for the first time language about mobile devices, which are rapidly becoming the most common way to use Facebook, Twitter and similar services.)