Of course, the fallacy in this thinking is that (since the fossil record shows wonderfully-adapted creatures all through it) that 'less-adapted' creatures never gained enough numbers to be represented (which is DonaldC's point).
It truly is impossible to falsify a theory that actually predicts that the evidence to support it should not exist.
"You do see fossils of animals with deformities (including humans and their ancestors). You see them alive and running around today, why would think that they didn't exist in the fossil record?
Anything that was truly not viable would be limited to a single isolated individual and hence you would expect to find them fairly rarely, but they do exist."
It just seems to me, and I am not an expert in the field, that there should be a huge quantity of examples of random mutations, viable or not, relative to what would have had to occur on the scales we are talking about.