I always supported PBMining but unfortunately I now think this was a ponzi and here is why I think this: it is too big of a coincidence that PBMining collapsed after a series of very low difficulty increase and a difficulty decrease. When the difficulty was up, people were not able to recoup their investment because of this and PBMining just gave you back, week after week, part of your investment. You would have lost money but you would have been "happy" because this was the difficulty's fault. The profit he was making was needed to pay the clients who, through referral link, got more GHS than what they paid.