Bitcoin can be usefull for the economy if it will adopt totally by one country and allow it to become useful like for online payments and can be use to buy online goods and services freely like how we use our fiat money. Although in my country we already use it to buy loads and pay bills but i think it's not yet enough to say that it was good to the economy. It needs more improvement and development. Maybe after a couple of years,who knows it might happen to become or consider as a secondary to fiat currency.