One of the points that comes through in looking at the comments in response to my plausibility survey (preliminary results here) is that for many, the various aspects or events in life's history have very different degrees of plausibility from an evolutionary perspective. It seems that many scientists are willing to accept that evolution explains all of the history of life on earth, even though the concrete evidence for evolution is largely restricted to microevolution. They take that evidence and extrapolate the rest.
I think that mental step is extrapolation error. There are enormous differences between the microevolutionary changes that we observe occurring and the huge leaps we see in the biological world around us and in the fossil record at other times in the earth's history. Minor changes within species are very different than the creation of entirely new body plans and complex organs. It is illogical to conclude that proof of what caused one is proof of what caused the other.
Michael Behe gets at this idea in this recent post:
The authors remark, “The evolutionary puzzle becomes more complex at a higher level of cellular organization.” No kidding. Nonetheless, they, like most Darwinists, assume that larger changes involving more components are simple extrapolations of smaller changes.
This kind of weak logic would never fly in other scientific fields.