Online gamblers in the U.S. have tended to use Circle.com and Coinbase to buy and sell their BTC because these companies allow easy integration with U.S. bank accounts. In just a couple of clicks you can move dollars from your bank account to and from their online wallet. Unfortunately, Circle have just announced that they are removing the ability to buy and sell bitcoin via their website and app. Coinbase is now the easiest option for U.S. based gamblers to buy and sell bitcoin. Coinbase do monitor for online gambling related transactions more thoroughly and have banned many uses for using their service for sports betting, poker and other gambling related purposes, so it's important that you use a middle-man wallet. More information here - http://www.bitcoingambling.io/choose-a-wallet.html A couple of weeks ago we reported that the IRS are in a legal battle with Coinbase as they try to force them to hand over all their customer's information. This may have prompted Circle.com to withdraw BTC buy/sell features in an attempt to avoid expensive legal battles.