If you think of "education" as the provision of information, then yes, the Internet is "replacing teachers". However, it is really not doing anything different than books, video and audio; none of which has replaced teachers.

There is a social component to education, the interaction with those who have more experience and yes, knowledge, that a computer cannot match. Even with a memorization-heavy subject like history, you still need a teacher, if for nothing else, to help sift through and analyze the mass of information and interpretations now available.

Remember, we went through similar predictions with videotaped lessons, before that, televised lessons and even before that, correspondence courses. However, the completion rate on these are dismal, because people need interaction and structure at the very least.

Rather than thinking of technology as replacing teachers, it is radically challenging teachers and educational institutions, not so much because that it is providing information in a radically different way, but because information is now ubiquitous. If teachers and schools dont exist simply to provide a set of information to learn, what should we be doing? There is no clear answer, but from experience, I do know it will require being a LOT more active and interactive than it used to be. If students are going to plunk money down for formal education, those hours in the classroom need to count for a lot more than they use to.

As for Wikipedia, I dont see the educational value in it so much as the technology, but rather that it provides an opportunity for students to "apprentice"  especially from my point of view as a language teacher. Students are creating and modifying texts, which are not simple exercises but the "real thing" with real consequences. And not just texts, but other forms of media such as video and digital animation.... Wiki Learning is doing a couple projects of this type as we speak now.

However, none of this indicates that working with Wikipedia means a purely online environment. Perhaps just the opposite. Creating Wikipedia content is not drill-work,but rather so-very human. With its mass of rules and norms, the involvement of someone who has experience becomes more essential. This is why very few new editors stick around and why the Education Program has the concept of Campus Ambassadors.

IMHO, technology is best used in these situations: to take drill work out of the classroom, to take lecture out of the classroom (flipped classroom) and to allow students to do activities that before were not possible before.  Wikipedia fits in the last category, because perhaps its greatest contribution to education is allowing students to publish work for the world to see within a community that is outside campus.

Leigh