Is there an actual, physical event associated with predatory conferences?
So far as I can tell, and have read online, predatory conferences typically are associated with an actual event.  

To my mind, this seems to be a key difference between "predatory" and "fraudulent."  If a conference takes your money and no event is organized, then there is clearly false advertising and grounds for legal action, perhaps even criminal charges.  If a conference takes your money and organizes a horrible, worthless, CV-staining joke of an event, on the other hand, there is no regulatory body that you can complain to: scientific quality is considered to be a matter of judgement, and there is no way to easily distinguish between an honest-but-poor-quality conference and a intentionally predatory conference.