@Yancey - You're right, it isn't and there are several conditions that need to be satisfied for the systems to switch to ground mode. It's important to understand that the <60kts rule was added to the spec regardless of air/ground mode though - it's purely because the AoA vanes' certification states that they cannot provide useful data below that IAS.
There was a lot of discussion over the relationship between that limit and the stall warning in the Tech Log threads, and the only thing that could be considered a consensus opinion was that it is a very tricky problem to solve. This is because a behaviour that may be valid in some scenarios would not be valid in others, and could be downright dangerous in many of them.
The take I came away with is that no matter whether your instrumentation is of the old "steam gauge" variety or of a more modern vintage, it can only provide useful information when inside the flight envelope, or to an extent when slightly outside. The further outside the flight envelope you go, the less useful some of the instruments and warning systems become.
EDIT : @BOAC - see my first paragraph. The <60kts limitation is not related to ground mode, and the designers made no such assumption. What they couldn't take into account was a scenario in which the aircraft was as far outside the flight envelope as AF447 became.
Last edited by DozyWannabe; 15th Oct 2013 at 17:12.