Coinbase has been banning user accounts that send Bitcoin to gambling sites, such as Satoshi Dice or Seals With Clubs. Earlier today a reddit user made a post stating Coinbase banned his account for allegedly purchasing cannabis products with coins purchased from the service. The user provided screenshots of email correspondence with the Coinbase support team, which states the remaining coins in the user's wallet may be withdrawn, but will not be able to utilize the purchase or selling services Coinbase provides.
Coinbase cites this decision was based on its efforts to stay in compliance with anti-money laundering (AML), regulations. These actions however raise concerns that Coinbase is tracing coins purchased through their service, and users' spending habits even after coins have been withdrawn from the online wallet. These actions can set a dangerous precedent for blacklisting unspent outputs involved in transactions with "suspicious addresses."