Authors like Hancock, Hoagland, Sitchin, Alford and the likes. Their views are of course extremely controversial and even scandalous since they go completely against the scientific status quo. Now, since I have read all these books, I cannot say I'm a firm believer in either side of the debate. The conservative scientific community has always been very methodic in its researches, and this is good.
Evidence is processed gradually until some ground-breaking theory replaces the one preceeding it.
Independent researchers however do not have this methodic approach. Upon the discovery of controversial evidence, they will immediately publish books with their new theories. And this is dangerous, since many of them are completely ignorant of other evidence that completely contradict their theories. And, worst of all, they will continue to publish books with ridiculous evidence simply to make a living out of it. Often, their first releases will be quite convincing since it is often the result of many years of research.