Having taught courses on the Internet as well as in the classroom, it depends on how the course is structured. For example, we ensure that the students participate in threaded discussion groups and in a chat room class each week. There are assignments and papers as well. We have actually discovered that the students appear to get more involved in the learning because of the distance. The threaded discussions allow us to explore a number of topics that can't be done in a regular class because of time constraints.
Students can also access the library and other search engines to supplement their learning.
Now if we just hung a course on the Web and gave students months to complete it and there is no interaction, we might question the quality. That is no different then allowing a student to take a year to complete an oncampus course or a video-taped course. The Internet is only a tool for allowing students to learn. It isn't the end result. It does take a different perspective for a faculty member to develop and teach on-line.