Jan 25th COTH had an article about a proposal by the FEI to establish a working group to investigate air vests.
One thing that strikes me is that the nay-sayers always have things that may happen - damage caused by landing on the air canister, neck support may stop MIM helmets working properly - rather than investigating the experience of the many riders who used them and feel they have benefited. Maybe the only riders who appear in medical statistics are those that do e.g. land on the air canister because the other riders walked off sound.
It is obvious that the effectiveness/safety of air vests is a very difficult thing to research. They have been in use for several years but still no definitive standards have been achieved, unlike body protectors.