In a special series on "Welcome to the future", CNN reports on educators using 'Second life'. The story talked about
The three-dimensional virtual world makes it possible for students taking a distance course to develop a real sense of community, said Rebecca Nesson, who leads a class jointly offered by Harvard Law School and Harvard Extension School in the world of "Second Life."
Frankly, I don't see the value of holding a regular class in 'Second life'.
A real good use of 'Second Life' I know of is by Lars Lundsten (I hope I have remembered the name correctly. If not, my sincere apology) in Helsinki, Finland. He taught a course in Department of Commerce where the entire course was run within 'Second Life' and course participants ran virtual organisations and businesses within 'Second Life'. 'Second Life' is NOT used as a classroom, but a space where simulated business practices were run and experienced.
In parallel, a multimedia course by Owen Kelly, partnering with Lars Lundsten created all the virtual campus, houses, companies headquarters etc. in 'Second Life' as "virtual contractors" for the commerce students.
That's creative use of the new technology. Yet-another-classroom is definitely a poor use of 'Second Life'.