I have seen some medical doctors who in their desire to attend and present in conventions, fall "victim" in predatory conferences. Usually these conferences are poorly organized with a very small number of attendees and without proper scientific program.
This is also true for research publications. Since some medical doctors want to publish immediately and without the rigors of reputable scientific journal, they tend to gravitate to predatory journals which actually defeats the purpose of the research academe and pursuit of research knowledge.