government and maths again ! (Yes, its plural, i am in the UK)
Bitcoins are not considered currency in the US, as shown in the recent case where some cops bought bitcoins and claimed they were going to buy stolen credit cards with them, then tried to fit up the seller on money laundering charges.
http://www.theregister.co.uk/2016/07/26/ponzi_bitcoin_case_kaput/
The judge said bitcoins were goods. This is the line of thought for an auction.
However, there is an exchange rate for bitcoins, so an auction is relatively pointless as whoever bids 1c less than the current exchange rate will win. Anyone who bids over the current exchange rate, can't count and anyone who expects to get some kind of good deal has the time and money to waste speculating.