Senator Joe Manchin (D-WV) just sent a letter to federal regulators calling for a ban on the virtual currency Bitcoin. The senator says Bitcoin attracts and enables criminals even as its value to the US economy is "suspect, if not outright detrimental." The letter is nonbinding.

Senator Manchin notes this week's collapse of the largest Bitcoin currency exchange, Mt. Gox, but the letter seems to be motivated by the fact that regulators in other countries such as Thailand, Russia, and China are cracking down on Bitcoin while the US is sanctioning it. "I am most concerned that as Bitcoin is inevitably banned in other countries, Americans will be left holding the bag on a valueless currency," he says.

"Americans will be left holding the bag on a valueless currency."

This isn't the first time Senator Manchin has spoken up. Back in June of 2011, Senators Manchin and Charles Schumer (D-NY) urged law enforcement to crack down on Bitcoins and Silk Road, the Bitcoin-only digital bazaar where illegal drugs were bought and sold. Silk Road was eventually shut down by law enforcement. It's unclear whether that public letter had any impact, but at the very least the senator's repeated effort to take down Bitcoin has identified him as a target for the loyal cryptocurrency community.

"I just called his office and told him that I would have to lay off my entire staff if Bitcoin was banned ... kinda an exaggeration but he needs to know that Bitcoin is being used in the United States for positive things!" one user commented on the Bitcoin subreddit.

Senator Manchin's letter was addressed to US Treasury Secretary Jacob Lew, Federal Reserve chair Janet Yellen, Comptroller of the Currency Thomas Curry, Commodities and Futures Trading Commission acting chair Mark Wetjen, Federal Deposit Insurance Corporation chair Martin Gruenberg, and Securities and Exchange Commission chair Mary Jo White.