It's bad for the velocity of the economy; holding a computer you're not using isn't great, but holding money you're not using is even worse, because by buying the computer you're sending out price signals earlier on that the rest of the economy can use to allocate resources appropriately. And deflation has a nasty tendency to form a self-reinforcing spiral (as does inflation to a slightly lesser extent, so the preferred approach is to have people actively adjusting interest rates etc. to keep a currency value reasonably stable but with a small rate of inflation).
The economy is not everything. It's better people use their money more rationally, rather than buying junk that they don't really need, which then falls apart and poisons our soils and oceans.
Plus it's quite clear to me that people are willing to spend their deflationary currency on the things that they believe in - the whole ICO market demonstrates it.
Not really - ICOs are just buying other, more deflationary cryptocurrencies.