[Air-L] Ethics in online virtual worlds

I will be interviewing and observing avatars within Second Life as research for my phd. I have been asked by my ethics board to obtain hard copy signature consent from my participants rather than online digital consent. Can anyone direct me to literature pertaining to the practicalities of informed consent in online virtual worlds (mmogs, mmorpgs, second life, etc..) or discuss their own experience with this? Thank you, Kevin