A user of TalkBitcoins.com wrote in today with this question, and I personally have dealt with the same issue with my small hometown bank:
Bank questioning my Bitcoin purchases?
Hi, my USA hometown bank called me today and was questioning me about my Coinbase/BTC purchases. It was their security and fraud department. They were asking all kinds of questions about why do I buy them, what are they used for, and also mentioned how BTC are very involved with terrorism and money laundering.
My question to you guys is, what is the typical reply you think Coinbase customers should use? I really felt pretty violated that my bank, or any bank for that matter would be asking these things from me.
So does anyone know when and what guidelines are being put into place to help out banks and customers fix problems like this?