Thanks for finding and posting this Aaron - a very useful commentary on some of the things it is useful to know for anyone thinking of building student activities. There are some very helpful recommendations and resource lists here and it does discuss other virtual environments, not just Second Life.
Everyone - don't be put off by the rather academic introduction! This is easy to read, clear and useful. I am sure it will answer some of the questions that are running through your mind as you contemplate the possiblity of using Second Life with your students.
Clare