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).