“For example, under a law recently approved by the parliament of the United Kingdom (the first country to sign an IGA), HM Revenue & Customs commits explicitly to impose the American FATCA law on British institutions. The costs of regulatory implementation by HMRC would fall on British taxpayers. In turn, UK financial institutions (and their customers) would bear hundreds of millions of pounds in costs for collecting the information for transfer to the IRS. The direct revenue benefit to the Exchequer? Zero. What is the U.S. obligated to provide in return? Nothing, as it happens. The IGAs have no clear status in American law.”
http://www.neurope.eu/article/fatca-will-europe-pay-price-one-sided-us-financial-information-demands