Yobit being a Ponzi is a matter of perception. Ponzi scams offer you "guaranteed returns" Yobit releases coins that act rather like a game or gambling. You are made aware of how everything works unlike in a ponzi which you are lied to about. That "10% per day" was 10% tokens per day, not fiat value. Just because you have 10% more coins doesn't mean you have now gained 10 profit. It could also be argued that users wearing mixer signatures are also supporting something that could be considered criminal. I have never had issues with yobit. I know some people have but we don't know their exact circumstances and all exchanges have bad things written about them. Even a very good exchange will have someone that doesn't like something or another.