There are a lot of questions here on what predatory journals are, and how to tell if a journal is one or not.
Are there known cases where a journal has "switched" camps, or where substantial evidence has been presented that they have? That is, has it ever occurred where:
- A journal developed a strong reputation for being predatory, recognized this, and engaged in a good-faith process of reform, eventually gaining at least a non-trivial amount of scientific credibility or impact?
- A journal with no history of predatory behavior suddenly started showing signs of becoming a predatory journal? For example, a publisher may have fallen on hard times, or been scooped by wealthier journals, and decided to lower their standards to such a level as to become predatory in order to survive.
For example, if someone has claimed, "The Podunk University Journal of Advanced Best Practices in Intermediate Spline Reticulation used to be a low-impact but serious journal, but after Podunk U was rocked by a cheating scandal in 2003 and there was a gradual movement away from Spline Reticulation toward Spline Retransmogrification from about 2005 to 2010 with a corresponding drop in the number of serious papers on Spline Reticulation being submitted, they started becoming a 'pay for play' publication and nowadays mostly publish incomprehensible screed written by rich patrons who want to increase their publication count.", that would count.
As the definition of a "predatory" journal is somewhat vague and based on professional judgments rather than 100% objective criteria, I would consider any of the following to "count" as a determination that a journal is or is not "predatory":
- The journal's practices or policies are so blatantly predatory or non-predatory that a conclusion is self-evident.
- A large-scale consensus exists on a journal's nature, even though there may be a minority that has raised a legitimate case for the opposite conclusion.
- A substantial, notable professional opinion has been released concluding that a journal is/was or is/was not predatory at a specific time. Inclusion on Beall's list would count as a professional opinion that the journal was predatory at the time it was added.