Now does hoarding hurt the usefulness of bitcoin ?
I'm not sure how saving money hurts an economy. Whether bitcoins are increasing or decreasing in value, I still have to purchase food, water, etc. Even for luxury items, I'm not sure if it makes much of a difference. If prices are rising, I may believe they have plateaued & choose to buy my boat now. If prices are falling, I may believe they will continue to plummet so I want to buy my boat now. Assuming bitcoins increase in value forever because they are deflationary, there are other factors that will make me want to purchase the boat. Summer may be coming, the family would really enjoy it, or I'm about to retire/quit my job, etc.
There are also huge benefits to hoarding/saving. The inflationary nature of dollars force people to make risky investments to fight inflation or risk their savings becoming worth nothing. So people either lose their money in risky investments or decide to spend their savings now before it buys even less. Now none of these people have any savings for retirement or hard times. Maybe a deflationary currency is exactly what we need to spur savings & eliminate the need of so many welfare programs.
at the moment ,there is so little places accepting BTC ,what else can you do with them ?
I agree with CoinCidental that it is easier to hoard bitcoins right now because there's not much to spend them on. And if anything this is driving the price up which is giving bitcoin more attention. But just like the bubble last summer, there will be a value where people will stop hoarding & start selling. Is this creating a lot of volatility now? Sure. Will this get ironed out? Absolutely. The higher the price, the more attention, the more merchants start accepting bitcoin, the less volatility there will be. This is all part of the chicken & egg situation new ideas face.