NeuroDojo: How much harm is done by predatory journals?

" ... To listen to some of these, you could be forgiven for thinking that publishing a paper in one of these journals is practically academic miscondusct: a career-ending, unrecoverable event. I talk to a lot of working scientists, both online and in person. And in all of that time, how many scientists have I heard of who have reported someone who submitted to one of these journals, who were not satisfied with their experience? Three. One experience is described in two posts (here and here), and a couple of others were tweeted at me when I asked for examples. And two were “my friend” stories, not personal accounts. For the amount of handwringing over predatory publishers, this is a vanishingly small number. Of course, these numbers are probably underreported, because nobody wants to admit that they published in a junk journal. It’s like admitting you got taken in by an email from someone claiming to be a Nigerian prince. It’s embarrassing to admit when you should have known better ... Assuming that the author has not gone into great financial hardship, let’s say the paper is published online, but without proper peer review. What are the possible outcomes, and what harms might arise?  If the paper is competent, the author could harmed because people will not read the paper because of the journal. But the paper is available for other researchers can use it and cite it if they so choose. People cite non-reviewed stuff all the time (conference abstracts, non journal articles) ... Another argument is that the harm of publishing in predatory journals is that the public or the unwary will be confused, because the findings could be untrue. Let’s examine a few scenarios of how findings could be false. The research was not done well. This is no different from research published in other journals ... The researchers are malicious. It is possible that someone with an agenda might try to give dubious information some sort of veneer of respectability by publishing it in a predatory journal. But... why? There are many easier ways for people with an agenda to spread lies than publishing in a crummy journal ..."