Back in the day, there was a decentralized trading platform called Etherdelta where you could find many ERC20 tokens not listed on any centralized exchange. Anyone could come to Etherdelta, add their own token, and even create a kind of market with unique buyers and sellers. You didn't need to ask for permission to start trading there, you could frictionlessly import self-created or someone else's token. No wonder this place was full of scams, malicious copies, impersonators, and useless shitcoins of zero value, but at least no one could steal users' data or private keys because of the decentralized structure of the said platform. However, the chief problem of decentralized platforms like Etherdelta is that they are (or may be) decentralized only on a technical level but not on a social one. Etherdelta had a founder, a single point of failure, who was charged by the SEC with running an unregistered "decentralized" platform.