From Business Insider:
The TSA attempted to "screen" airline passenger Davi Barker for the virtual currency Bitcoin.
Barker is co-founder of BitcoinNotBombs, a Bitcoin advocacy group that gets donation-based organizations and social entrepreneurs set up to handle the currency. He's written a very detailed telling of what happened right here. After going through security (he opted out of the body scanner but was successfully cleared through the checkpoint), two people stopped him, and it got uncomfortable quickly.
I was about to ask for my attorney, who happens to be my wife, when [the person wearing] the orange shirt said, “What about Bitcoin?” I was flabbergasted. This was above and beyond any scrutiny I had ever received from the TSA, and a little frightening that they were looking for Bitcoin. I said I didn’t understand the question. He continued, “We saw Bitcoin in your bag and need to check.” I was incredulous, and asked, “Do you have a superior officer because I don’t think you know what you’re talking about.” The blue shirt replied by repeating that they were “managers,” but if I didn’t answer his questions he could call law enforcement and have me taken into custody. I asked, “Aren’t you law enforcement?” and he replied, “No we’re with the TSA.”
If this sounds weird to you, it's because it is. Bitcoin is digital and doesn't exist in the physical world, to "see Bitcoin" in a bag would be like seeing email in a bag. What the agent more likely saw, says Barker, is the orange Bitcoin logo sweatshirt Barker was wearing at the time, promo material for his organization's annual "Hoodie the Homeless" drive. It looked like the one pictures above.
It's illegal to leave the United States with more than $10,000 cash, so the TSA is likely interested in Bitcoin as a means of sneaking money around for nefarious purposes. But Barker was traveling domestically, from Manchester, N.H., to San Francisco, and discloses that he didn't have nearly that much, Bitcoin included.
Whatever your involvement in the virtual currency, it may be wise not to mention anything about Bitcoin during your next airport security check.