If the valuations were to be found misleading, the valuer could possibly be sued - even with all of their disclaimers etc. I doubt many valuers would risk ruining their reputation. Their biggest clients are the banks and financiers.
They are fairly clear about what discount rate they use. Obviously there is no magic way to predict the future cashflows perfectly, but I doubt they will be out by 50%.
I will say that term deposits have a lot going for them as far as avoiding losses is concerned. lol
FKP Price at posting:
$1.20 Sentiment: ST Buy Disclosure: Held