Just 'cause a paper's in Science [Nature] doesn't automatically mean it's wrongIn all seriousness, while those two journals have published a lot of groundbreaking work, a disproportionately large fraction of what gets published there turns out to be crap. The reason is that these two journals evaluate papers differently than other journals. Science and Nature put a high premium on newsworthiness, while most other journals do not. As a result, people trying to get their papers into Science or Nature often "sex up" the paper's conclusions a little further than perhaps the data warrants. And the most speculative papers are often the most newsworthy --- but also the most often wrong. A final problem is that the strict length limit means that many details of the analysis must be left out (this is less true now that details can be put into electronic supplements). This dearth of details hinders the identification of problems by peer reviewers. Thus, I would tend to agree with the views of the Capitol Hill staffer described in this Prometheus post:
An interesting detail was that one staffer spoke about a "discounting" of scientific results conditional upon in which journal the result was published. Science is associated with a low level of credibility whereas GRL is considered a generally "good" source.