Why you want relaxation for this particular income. I see  it nothing different from other types of income and thus it should be taxed as well. There is only one difference that any government is not spending anything on the development or promotion of bitcoins and thus it might appear illogical to some people that they are taking tax for this income. But the problem is that if there is relaxation for a particular income source, all people will start keeping all money there. This also applies to big companies and they will start charging in bitcoins to save tax.