The real problem, in my opinion, is the idea (under development for decades) that the correct way to govern is to ask the experts in their field what we should do. So we turn to the climate scientists and ask not just "is the Earth warming?" but "what should we do to stop it?" We turn to social scientists and ask not just "does television affect test scores" but "what sort of television should we regulate?" We turn to other scientists and ask not just "what is going on" but "how should we fix it?"
When we hand any group of people that sort of power, of course people who are attracted to power are drawn to that field. Not only do we get cranks who claim to be scientists attempting to drive the conversation (such as those so-called "researchers" who periodically pop up and tell us pornography leads to rape), but we also subvert the real Ph.D.s.
Science should be in the realm of explaining what is going on. But deciding what we should do about it belongs strictly to the realm of politicians. Scientists may be asked for their input ("will policy A or policy B be better?"), but they should not be creating, driving, or steering policy.
In the case of Global Warming, the real problem (in my mind) was that these guys were also neck-deep in the UN's IPCC process, which is drafting treaty proposals on the economic changes that the world should make to fight global warming. By being neck deep in the politics, and by believing truly that we must act now to combat global warming, the incentive became about the power and honor of belonging to the IPCC and to help drive policy--not to get the best data possible from multiple disciplines and share that data with other scientists who were experts in those disciplines. The incentives, in other words, was to prove certainty about Global Warming to help drive IPCC policy, not to distribute data and allow uncertainty to creep into the proxy climate studies--such as tree ring studies, which are inherently messy and uncertain.
I suspect that trust in science has been eroding for as long as we've been asking scientists to play politics. This isn't the start of the avalanche; it's just a major slide in a problem going on for a very long time. And it will continue to get worse so long as the airwaves are populated by charlatans pretending to be scientists attempting to drive policy (like the anti-porn, anti-second-hand-smoking, pro-organic farming, anti-pesticides guys who, after affecting change, are proven after the fact to be fakes), and so long as politicians, attempting to keep votes without having to put his neck on the line, continues to subcontract his job out to untouchable "experts" which he can blame for any failures. (Well, I was told...--don't blame me.)