OneCoin was a cryptocurrency Ponzi scheme. It was launched in 2014 by Ruja Ignatova. Investors lost over $4 Billion in the OneCoin scam. The scam attracted many investors through many launches. Ruja convinced many people in 175 countries to invest in OneCoin, promising them big profits. OneCoin claimed to be a cryptocurrency that would change the world for the better and help connect different blockchains, but it never even had a blockchain, it used flashy marketing and MLM (Multi-level Marketing) to incentivize people to sell to friends and family, and since the project didn't have a blockchain, it was not on any exchanges, it had it's own platform. In 2017 authorities found out that it was all a big scam and Ruja Ignatova has been missing since then, and her brother, Konstantin Ignatov, who took over as CEO was arrested later when he pleaded guilty of being involved in the scam.
