There are two types of predatory publishers:
1. The truly predatory. These are the guys who build a website with the same name as a real journal, copy its editorial board and wait for scientists to make a mistake (this is journal hijacking). Or who have conferences with a similar name or a fake organizing committee.
These are publishers preying on trusting authors. This is, probably, the minority of predatory publishers.
2. The low quality (or perhaps no quality) journals. This is what most of Beall’s list is actually about.
In this second case, it is the publishers and the authors preying on the scientific system and often preying on taxpayer’s money! The authors are accomplices and not victims of predatory publishers.
The people who submit to these journals generally know what they’re getting. Or at least they should know.  An author who submits some mediocre poems as a research article cannot be deluded (ht Jeffrey Beall).
If you are at a third rate institution with third rate supervision and your work is third rate, this is win-win-lose: you win because you get a publication (which you can tout to your funders), the publisher wins because they get the publishing fees. The taxpayer loses twice: once for paying the publishing fee and they lose even more if this outlet is an excuse for you to not do the kind of good work that would get you in a real journal.
This is, naturally, a bigger problem at non-first world institutions . The work is not as strong and the supervision is weaker, thus you can fool the bureaucracy by pointing to all of the shitty not-really-peer-reviewed papers you published (or the bureaucracy understands and helps you fool the politicians; it’s fools all the way up).
However, it can happen in the US as well. The story of Western Illinois University seems to be similar: the professors knew they weren’t really getting peer-reviewed, the union knew, the departments knew… Everyone still went through the motions to be able to claim that our faculty publishes needs two-peer peer-reviewed journal publications for tenure . The fact that it was a private institution does not change the basic point that it is the taxpayer paying. Its college students get taxpayer subsidized loans and they may get some public research money as well (which go to pay for these publishing fees). But of course, the students are getting ripped-off too.
Most authors of “predatory journals” are not victims, they are predators themselves. The taxpayer and society are the victims.
||There is always the possibility of publishing in a barely-known journal that’s starting out because you think it shows promise and later realizing that it is actually a bad journal with little peer review. You can minimize the risk for it by looking at who is the editor, &c; but sometimes you might really make a mistake. This is not what we are discussing here, though. I have also heard people argue that 10-15 years ago, some people really were fooled by low-quality conference invitations which then required some payment as they were too trusting. This was understandable then when you got your first low-quality invitation, but nowadays people really should know better (I, as a lowly postdoc, get plenty of invitations to shitty conferences, I can only imagine how many real faculty get).
||I might get some pushback on this, but seriously: a country that had strong institutions and, on average, good work would be a first world country. That’s what being first world means! (Yes, there are exceptions; but there are more problems in non-first world countries).
||Read the second comment by Robert J. Hironimus-Wendt on this page Even as he tries to defend the school, what becomes obvious is that the standards are shoddy.