I personally think taxing biycles at this time when we are working hard to encourage more people to bike is not a good idea. Remember that when someone rides a bike, he/she eliminates many externalities (environmental cost, congestion cost, health cost, etc) from his/her commute. So we can argue that car drivers only pay a small amount of tax for mainly road maintenance but never pay for the externalities they create. Therefore, cyclists are already "paying" by saving.
Last week Democrats in the Washington state legislature introduced a $10 billion transportation package with a number of revenue elements. According to the Seattle Times, the proposal increased the gas tax by 10 cents every five years until it reached nearly half a buck per gallon, created a "car-tab tax" for .7 percent of a car's value, and a $25 sales fee on bicycles that cost more than $500. The latter item was included as "a nod to motorists who complain that bicyclists don’t pay their fair share."
As one might expect, the reaction from bicycle bloggers was swift and sharp, with Streetsblogcalling the bike tax "pointless." A number of strong counter-arguments were raised in the discussion. In explaining why the tax "simply makes no sense," the Seattle Bike Blog pointed to a study showing that riding actually saves local governments money. Cyclelicious noted thedisproportionate nature of a bike tax compared to the excise tax on new vehicles purchases.