As a (Danish) student of political science I have some idea of what happens on the other side of the monitors and I have to say that mostly people really are writing notes and listening. Sure there are some who can not stay away from their IM, especially if it’s the new boy-/girlfriend who is writing. But in general most people use their laptop for writing notes and occasionally checking mails or the like, which probably is not a problem since few people can stay concentrated on difficult material for 45-60 minutes straight. It might even be good to switch attention to something else for a few minutes and then switch back again.
It might be different here in Denmark, but I don’t think you have reason to worry. Most university students have an interest in learning. If you were teaching high school students it would be a very different case – trust me 
Furthermore, it is not that easy to watch YouTube or the like if you are not wearing earplugs and that would look strange at a lecture.
