I doubt US based exchanges have guidance yet - or we would see it as the only guidance they could rely on is a private letter ruling.  IRS private letter rulings are made public.  I can also easily understand why the IRS is not ready to weigh in on this yet - we're still sorting out what bitcoin is ourselves.  From a policy perspective, it is sad that the IRS is in this position.  

Virtual currencies predate bitcoin by over a decade.  The IRS hasn't given any 'safe harbors' for those of us who are willing to do the right thing.  Then again, they have not aggressively pursued the arena that I can see.  I see no court cases or taxpayer challenges.  What a mess for the IRS to have a judge decide how virtual currencies will be taxed.......

It would be nice if the service were to issue  'temporary' guidance while this virtual currency space works itself out.  Many are in for the investment - more like gold.  Many are in it as a currency - to support a consensus based transactional medium.  

As a miner you face, from a cerebral standpoint, the more discrete but interesting judgments..... do you recognize for tax purposes the coinbase when it is awarded or when it is spent - do you recognize it as of the date you become a part of the block-chain, at a safe margin of confirms or at the 100 confirm requirement for spending?  This stuff was pretty inconsequential when it was a $750 issue when this year began.

And since the block time stamp is not an indicator of the time of the coinbase award or its confirmation, tracking will be interesting....

And what do you use for valuation - interday average on Mt. Gox, Bitstamp.... some blend, some running average..... ?

Take heart, though, as your issues are pretty obvious and you have lots of options that are rational and will not be a compliance nightmare once they are made.  I am dealing with a bigger issue right now on those who are determined on using bitcoin for purchasing transactions in a business.  

We are facing some very real compliance issues not only for valuation but also for accounting where bitcoins are regularly used in purchase transactions by a firm...... say you bought your bitcoin for $100, then you used it to buy a portable computer.  The portable may be $800, so there are two transactions here - you made $700 on your bitcoin, you purchased an asset...... Straight forward transaction, but for an individual using Quickbooks (or big boys on an Oracle or SQL solution), it's not easy to track without double entry, and double entry is twice the work.......

All the luck Raize.  Congrats on having the problem you do and I hope you 'ASIC Up' as a friend says, the market only appreciates for bitcoin, and your problem is only worse next year as you pocket some coinbase.......  ditto for you Goat - and I want a ride in that new car.......