As both a teacher and a recent student: you do not know what the student is doing on their laptop, nor is it your job to police what they do on their laptop; some students are using their laptop to enhance their learning experience, and some students will have come to rely on that enhancement... and frankly, even if a student is multitasking, maybe they have a very legitimately pressing reason in their life to do so today.<p>If you really wish students in your classes would multitask less than they have been, you should concentrate on adopting a more focussed pacing for your content, and you should figure out how to make your material more engaging (which you can do either by making it more interesting or more entertaining: I will ask that you avoid cheap tricks like putting students on the spot and trying to scare them into paying attention).<p>As for the effects on people using laptops on the people around them, there is also a simple solution I have found quite effective: make a culture where students who are unlikely to be paying complete attention to your lecture sit together in the back of the class. As both a student and as the teacher, I have found myself completely forgetting about the existence of students who are sitting far in the back who might be distracted.