Fungibility is an advantage Monero has over Bitcoin and almost every other cryptocurrency, due to the privacy inherent in the Monero @blockchain and the permanently traceable nature of the Bitcoin blockchain. With Bitcoin, any BTC can be tracked by anyone back to its creation @coinbase-transaction. Therefore, if a coin has been used for an illegal purpose in the past, this history will be contained in the @blockchain in perpetuity. This lack of fungibility means that certain businesses will be obligated to avoid accepting BTC that have been previously used for purposes which are illegal, or simply run afoul of their Terms of Service. Currently some large Bitcoin companies are blocking, suspending, or closing accounts that have received Bitcoin used in online gambling or other purposes deemed unsavory by said companies.