Encourage passive learning
Depending on the level of interaction in the classroom setting, shy students may be allowed to attend classes without providing alternative ways to communicate ideas. Forcing students to learn by vocal exchange with a professor may limit their ability to learn.
Ignore individual learning differences between students
Classrooms environments tend to group students together in large number often making it difficult for instructors to isolate learning deficiencies and provide the necessary close attention that individuals may need to learn. Online classes allow for a more individual persepective from the professors standpoint due to most of the communication being easily handled through email and chat.