I've remotely participated in several IETFs.
I find that the biggest problem with remote attendance is the lack of
visual cues. I've come to realise just how important these are in a meeting.
-are people paying attention, are they interested / confused /
distracted / bored?
Also there's no way for local attendees (in the WG room) to know that
remote attendees are "at the mic" and whose turn it is to speak.
There's been some discussion on the "87attendees" mailer about badge
sensing at the mic - whether QR codes, NFC, or RFID. This could help
remote attendees too.
eg, see what they did with NFC + mic here:
http://www.5thbar.me/blog/2012/09/14/nfc-enabled-badges-at-the-5thbar-mobile-marketing-forum/
P.