ALK A343,
There is a reason why the Airbus reverts to alternate law with unreliable speed. It actually happens to make the pilots job easier, since you can't trust the airspeed indications, you have to fly pitch attitude and thrust setting.
The last thing you need in this situation is for the overspeed protection to activate and the aircraft to pitch up on its own, that is why the switch occurs from normal law to alternate, because in this situation it is the most appropriate control law.
Point taken, and from what I understand it indeed looks like the best option by far.
Actually, I am much more surprised by what I've read regarding the Quantas incident: is this pitch down a situation where the switch from normal law to alternate law did not happen soon enough? My apologies if I misunderstood this report, which I went through rather too quickly:
http://www.atsb.gov.au/publications/...70_interim.pdf