Frdsmth is partly correct. Forming student/professor and student/student relationships is crucial to education. But he/she is wrong about this not being possible at all online institutions. In short, some online schools have technology such that there is direct, live "real- time" interaction between the professors and students and among the students.
One online law school, where I attend, has this technology, namely the California School of Law. The School's website describes how this works:
"Students can speak with the professors and classmates by logging into a Virtual Classroom from a computer at home or work, to discuss cases and debate the law. The virtual classes meet each week on Tuesday and Thursday evenings, with students participating in live law school classes, where students can submit examinations, essays or memoranda of law for professors to grade, as well as study groups to discuss cases, trade class outlines, prep for tests and make friends and networking connections that last a lifetime."
One of my classmates is quoted as follows on the school's website: "The courses are taken in the convenience of your own home, yet you are able to interact with the professor and other students as if you were actually physically present with them in the classroom." Dana 1L