I bought a house in Melbourne for 605k MAR 2007. Just had it revalued last month for 700k, and that was without the bank getting a valuer to turn up - they do it just off internet sales.
in the current climate, I don't think that they will seriously look at revaluing property where I have bought.
But then again, I only have a 60% loan. Maybe the banks will get nervous for the people in the outer suburbs that owe 90% on a $400k house that is no longer worth 400k.