All of the receipts you send to them are also accepted by the IRS, so if you are ever audited, just show the images of your receipts from your account.
But unless and until Bitcoin can be used to buy a sandwich, or be accepted by your friends when you pay them back for a restaurant meal, then it is likely to remain just a playground for geeks and gamblers.
By holding back from TV and concert appearances, the group and its management went against the industry-accepted wisdom that you can only hold fans' attention by plying them with nonstop appearances and regularly dispensed songs.