Irish Steve,
BA have been using online check-in successfully now for about a year and it has been introduced more or less worldwide in that time. BA customers (except ex USA where they must ID themselves to a member of BA staff at checkin) can proceed all the way to the gate without having to show any ID to anyone. Whether you think this is right or wrong, it has obviously undergone thorough checks and has had the sign off from the airline and airports security experts otherwise it would not be happening.
My worry would be if the staff at the gate (in the case of FR the cabin crew) are not checking the ID's as the pax board the aircraft.
Having spend three years working on the ramp in DUB both before and after 9/11 I too am all too aware of the security loopholes in the airport (remember that landside lift beside Hughes and Hughes where one could get into the baggage hall without a security and check in agents often took passengers down if they left something in their luggage that they needed?
) but I am also aware that there have been major improvements since and I dont feel that the online boarding pass is a big threat to the airport.