You know what else is deflationary? Electronics. Why buy an iPad now when it's going to be 30% cheaper next year? The money used to buy electronics is extraordinarily deflationary -- yet people buy electronics all the time! They should be hoarding that money, wait a year, then they can get 30% more electronics with the same cash! I don't know why anyone would buy electronics, then. Oh, except they do. And somehow that market is freakin' enormous, contrary to the economic theories.
As a matter of fact, deflationary expectations kill trade in electronics too. When a company announces a revolutionary product just around the corner, customers cease buying it's current inventory and hold out for the latest and greatest. Sometimes the revenue hit is so strong that the company folds before the revolutionary next version has a chance to become reality, as was the case for the Osbourne Computer Corporation. The phenomenon is called The Osborne effect, has been observed since in many cases, and is a textbook case study in technology marketing.
That being said, this sort of thing does not usually happen for electronics, although customers know and expect constant advances and lower prices. That's because the electronic device provides an utility to it's buyer since day one, which might very well be above the present value of money for that person. If I want to make pictures in my vacation, I will buy a digital camera today; although I might get it 20% cheaper a year later, I would have no pictures from my vacation and that loss is not compensated by the 20% cheaper camera. In the long run we're all dead.
Since a speculative asset like Bitcoin derives no utility for it's owner, this - often repeated - analogy is flawed.