I think that there is a lot of difference in the problem of predatory journals than of predatory meetings.
For journals, we are talking about many who are truly unambiguous predators, where they will publish more-or-less anything for cash, capitalizing on many academic researchers’ desire to inflate their CVs, and often aid that duplicity by having names that mimic real, peer-reviewed journals. The consequences can be extreme, not only by the loss of research funds to this, but because of the unfair assessment made of some researchers’ productivity as compared with others for the rewards of career success.
Identifying predatory conferences, on the other hand, is more ambiguous and of less consequence, in my view. First, there is a gradual blend, I think, of legitimacy (whatever that means) for conferences, and very few of these criteria signal anything sinister in isolation. Secondly, a lot of it is a matter of preference for what the attendee wants to get out of a conference – Is it the chance to hear groundbreaking research, or to meet and interact with leaders in the field, or to socialize and network with colleagues and potential collaborators, or something else? Thirdly, the consequences of attending a less “legitimate” conference are minor, at least in my field. When evaluating someone’s CV, there is not more than trivial credit a person gets for showing up at a meeting and not even much more if they gave a poster presentation or a short talk. It just “checks the square” that they are participating in professional life, but isn’t really worth any big points. So what is the real consequence? I suppose disappointment by the attendee that s/he paid money for a disappointing experience where the presentations weren’t so good or the meeting not so well attended, but that can happen at the most legitimate of conferences as well.