What are the pros and cons of laptops in a classroom?
I think due to increasing lecture sizes, and in complex or technical courses, having something like a tablet or laptop is considerably useful!

There's something to be said of classroom etiquette, however, in that not everyone is equally courteous. Some big no-no's for most of my lecturers were: 

(1) No recording via the built-in camera, especially without permission, and no holding things up and taking photos. People learn in different ways, but we have to standardize the classroom somewhat, because not everyone can idly sit by and concentrate while 10-20 people are holding up their tablets, taking flash photos, or doing something otherwise weird/distracting to copy lecture notes. 

(2) If you have the slides up on your personal device, make sure it's the only thing you have up unless otherwise specified. No one wants to see someone elses Youtube, Facebook, etc. during the lecture.

Beyond that it is distracting to hear the tapping of many keyboards vigorously trying to take notes all-at-once. I think that these people do themselves a disservice by taking word processor notes, however, and that to a great extent hand-writing the notes even if you have a personal device helps to enrich you in the material. My personal method was laptop set to slides, write notes on paper. But again, not everyone learns the same way. At that, for some complex courses I constantly search terms I didn't understand or concepts I might have forgotten about so I don't get utterly lost in the process. To me this decreases the amount of hand-raising and review questions.

I think that having some ground rules, and a little talk about common courtesy in the beginning of the term is good. It's penalty enough for some people to get called out for being discourteous in front of the class, so a ban? Perhaps not. And like I said in the beginning, lecture sizes are up there and not everyone has choice hearing/vision, so laptops/tablets help supplement those people who can't see the presentation or can't hear the lecturer.