Predatory Publishing is on the rise. As more research is being published, as organizations require publishing for tenure or advancement, as funding agencies require publication, there are those who seek to make money off the unsuspecting author. These journals generally claiming high impact factors or peer review while close inspection proves otherwise. As more quality journals require authors to pay fees, it becomes easier for fake journals to proliferate, taking money from authors and providing instant (and non-reviewed) publishing.
There are a variety of reasons authors may publish in a predatory journal:
NIH linked information on publishing in authoritative journals.
Complaints that are associated with predatory open-access publishing include (from Wikipedia, see below)