Psychologist Peter Gray of Freedom to Learn reports:

How common is scientific fraud? Nobody really knows. Defenders of science’s purity often argue that such fraud is very rare, the product of a tiny number of “bad apples.” But I doubt that. My suspicion is that the cases of fraud that are exposed are just the tip of the iceberg.

… replication is rare in most areas of science. Most scientists want to do something new, and funding agencies rarely provide grants to repeat already published experiments. Even when replications are conducted and fail, there are almost always ways to explain the discrepancies without suggesting fraud.

This sentiment is echoed in a recent article in the Atlantic entitled “Lies, Damned Lies, and Medical Science“:

To get funding and tenured positions, and often merely to stay afloat, researchers have to get their work published in well-regarded journals, where rejection rates can climb above 90 percent. Not surprisingly, the studies that tend to make the grade are those with eye-catching findings. But while coming up with eye-catching theories is relatively easy, getting reality to bear them out is another matter. The great majority collapse under the weight of contradictory data when studied rigorously…

His model predicted, in different fields of medical research, rates of wrongness roughly corresponding to the observed rates at which findings were later convincingly refuted: 80 percent of non-randomized studies (by far the most common type) turn out to be wrong, as do 25 percent of supposedly gold-standard randomized trials, and as much as 10 percent of the platinum-standard large randomized trials. The article spelled out his belief that researchers were frequently manipulating data analyses, chasing career-advancing findings rather than good science, and even using the peer-review process—in which journals ask researchers to help decide which studies to publish—to suppress opposing views

As illustrated by Climategate and by scientists continually refusing to release original data, scientific dishonesty is rampant. Real scientists release data.

Gray and Freedman paint a bleak picture about the current state of science, and there is good reason to believe them. As government funding expands and personal powers grow more concentrated, people will fight harder and harder to reach the upper echelon of their chosen groups. Millions of dollars, unquantifiable power, and limitless prestige are all given to the top ranks of each field. It is all about statis. That is what drives Science, Politics, Business and any other field in which humans compete. The truth is often the innocent bystander that gets ignored.

Compounding this problem is what Arnold Kling identifies as inbreeding and what Daniel B. Klein and Charlotta Stern identify as groupthink:

At the very top departments, more than 90 percent come from the worldwide top-35 departments; the top is almost entirely self-regenerating. According to the regression line, the department ranked 100th would have about 65 percent of its faculty from the top 35.

When people say to “just trust the experts“, that advice should be taken with a grain of salt.