“The Treasury Department and the IRS have also decided that the risk of U.S. tax avoidance by a U.S. taxpayer holding an account with an FFI exists regardless of whether the U.S. taxpayer holds an account in his or her foreign country of residence or another foreign country.” The regulations say nothing about the problem of lock-out. They fix only on the unquantified and un-weighted risk that what must be a relatively small population of US taxpayers residing in a foreign country and banking at their local bank might evade US tax.