You're a voice of experience and reason @mrwalt. I lost some BTC back in 2014 in one these. It was easy to get seduced by the euphoria of quick and substantial returns, which ultimately came to nothing. At the time it wasn't a great a great loss if I converted to $, but now looking back if I'd just hodled those coins, well, you can guess the feeling.
I now attribute my 'loss' as a lesson learnt.
The lesson is simple - If it seems too good to be true, it is.
We have both lost money in this space and these were some hard lessons that forced me to learn the hard way. Now that I know what these things are I try to pass this information on and let people make the decision for themselves now that they have the information.