Interesting, since bitcoin's value is always rising, means most of the purchases made by bitcoin always result a loss, does it mean that people who spend bitcoin always receive tax deduction?
there are a couple of scenarios which probably apply
a) you buy bitcoins with fiat - the only thing that makes sense is to treat it like you would shares. when / if you cash out or redeem for goods / services you must claim any capital gains or losses.
you purchase 5 bitcoins at $100 USD then use / cash out when they are $120 USD you claim $20 x 5 = $100 USD of capital gains on your taxes. i don't think they would qualify as long-term capital gains so you get taxes at your regular rate - see
http://en.wikipedia.org/wiki/Capital_gains_tax_in_the_United_Statesin canada you are only taxed for 50% of your capital gains which is a little better. an interesting question will be if the IRS / CRA will treat bitcoins as investments - so for example you can include them in your ira (US) or rrsp or tfsa (canada)
b) you mine bitcoin - when / if you cash our or redeem for goods / services you claim the total value as income
you mine 5 bitcoins and sell for $100 USD each then you must report $500 USD income on your taxes - although I'm not sure how you report this - self employment income or 'other income' - they will probably need to clarify that