From Derek Lowe, who's spent a lot of years in "very early stage drug discovery," and who is both calm and reasonable:
It’s weird and startling, though, if you haven’t had the opportunity to go back through clinical research (and even patient treatment) and seen how many things looked like they worked and really didn’t. It happens again and again. Alzheimer’s drugs, obesity drugs, cardiovascular drugs, osteoporosis drugs: over and over there have been what looked like positive results that evaporated on closer inspection. After you’ve experienced this a few times, you take the lesson to heart that the only way to be sure about these things is to run sufficiently powered controlled trials. No short cuts, no gut feelings – just data.
(And who has a fine answer to the "Why don't we need clinical trials to test parachutes?" objection.)
From Alan Beard, who is "an international banker who finances highly structured multimillion loans in emerging markets for power projects, railroads, toll roads, port expansions, etc." and an adjunct professor at Georgetown:
Those of us who use computer modeling on a daily basis to assist in our analysis know how dynamic projections can be. These types of dramatic changes are routine when there are significant changes to the inputs that go into the models. In fact, that is the reason for modeling: determining the parameters of the inputs and how they affect the underlying outcomes.
Unfortunately, a superficial, agenda-driven press, which universally reports on outcomes from these imperfect tools as “settled science,” inevitably does a disservice to the casual reader in an effort to generate news and affect government policy.