"The United States has not denied a single extradition request from the UK under the treaty. While the U.S. does send more extradition requests to the UK than it receives, this difference is largely due to the differences in the size of the respective populations. The panel report notes that the U.S. has a population about five times the size of the UK, but there have been fewer than twice the number of people extradited to the U.S. than to the UK. The number of U.S. requests is not disproportionate."
http://london.usembassy.gov/gb140.html
"The United States has not denied a single extradition request from the UK under the treaty. While the U.S. does send more extradition requests to the UK than it receives, this difference is largely due to the differences in the size of the respective populations. The panel report notes that the U.S. has a population about five times the size of the UK, but there have been fewer than twice the number of people extradited to the U.S. than to the UK. The number of U.S. requests is not disproportionate."