- Professor was just regurgitating the text; student became bored
- Professor was not regurgitating the text; student lost the thread, became agitated
- Student did not understand material; student became frustrated; paying closer attention apparently did not occur to student
- Student's brain was full; student needed time to decompress
- Student was on a tight schedule and "multitasked", presumably so as to save valuable beer-drinking time later
I'm sure their parents are delighted to kick in that $40,000+ per year so their kids can ignore lectures whose content they could apparently have got on the web for free. I cannot help but feel, myself, that the Facebook-checkers are not the students whose needs I feel most strongly compelled to serve.