Critics of Second Life

Hi- I'm a virtual teacher who only has a bit of experience in SL. I'm doing some research about the debate over using SL in the high school classroom. I have plenty of names and titles for the pro side (which I assert), but I'm having difficulty finding academic references against the use of SL in the classroom (which I need for my paper). While it's clear what some of the potential fears are (cyberbullying, predators, etc), I am looking for scholarly reflection pertaining to this issue. Can anyone point me toward the critics of SL in education? Thank you in advance for your help.