The hoax email shows Bill Clinton having the highest IQ (at 182) and George W. Bush the lowest (at 91). The numbers claimed in the email were not backed up by any evidence but appeared plausible to some people. (Clinton's top ranking may have seemed more plausible due to his having been a Rhodes Scholar.) When the hoax was debunked, it appeared to many as a personal reproach on Bush due to its timing and the fact that Bush's IQ was reported as exactly half of Clinton's. Nevertheless, personal slurs upon sitting U.S. Presidents have been common fare in the United States at least since the administration of John Adams.
Perhaps because the issue of George W. Bush's intelligence has been a popular one, particularly amongst his political opponents, the hoax report was taken to be true in some quarters. The British newspaper The Guardian, for example, quoted the report in its diary section of July 19 2001 and used it to belittle Bush (see [1] below). The Guardian published a retraction two days after the Associated Press drew attention to the error.
Other mainstream media news outlets to fall for the hoax included Bild (Germany), Pravda (Russia), The Hillsboro Argus (Oregon, USA), The News Sun (Illinois, USA) and the Southland Times (New Zealand).
About.com reports [1] that linkydinky.com was the original source of the spoof. Indeed, their page on the hoax [1] calls the report "our spoof". A copy of the spoof in full can be found there.
The sociologists and institutions quoted in the article do not exist. The techniques used to measure the IQ of the Presidents are not recognized means of measuring IQs. The hoax contains other factual errors — see the Snopes article ([1]) for further details.