almost the same for me, except that if i read a book, i risk spending hours without paying attention to anything else, so no. 2 is also the reason why i don't watch half hour videos on youtube. but 3 and 4 happen anyways occasionally.

the problem is that with a book it's difficult to put down, especially mid-chapter. and with youtube videos i can stop after each video. (<- yeah right!)

solved it with audiobooks and making a list of shows i commit to watching when i have time, but no more than one episode per day.