I would agree that taxes are imposed on bitcoin transfers. If the tax is levied on the count of bitcoin income each month and takes a few percent for it, it will be a bit of burdensome. Better taxes are imposed on bitcoin transactions, for example 1% for each transaction.
Perhaps, although (and has been noted above) if the tax is too high for the transfers, the incentive to hoard the cryptocurrency increases and a fundamental principle or ideal of Bitcoin is hurt.