They are certainly causing CRM problems, the flightdeck is becoming "out of sight, out of mind" for a lot of cabin crew and I suspect the other way around for a lot of pilots. New video gear is making access a bit easier but IMHO the whole thing is a token gesture. If the CAA, Airlines and the DFT (bless em) where serious about it we would have El Al style double doors that actually do provide protection for the flightdeck.