I have taken the same view as my professors did in college. I stop the talk, and ask if the person would be better off getting wifi outside the room than in it.
Or put another way, your important time is worth just the same outside the room walls as it is in. The fact that you don't find the talk interesting does not mean you have the right to affect other people who might be enjoying it. [Especially the guy who took a conference call inside, but thankfully the other people were kind enough to take his phone and throw him out for me :)]