It turns out that it was owned by someone who wasn't just a Romney donor, he was a consultant for Romney:
A top adviser to former Massachusetts governor Mitt Romney appears to be behind today's launch of a new Web site attacking GOP presidential rival Fred Thompson.
The site, www.phoneyfred.org, paints an unflattering picture of Thompson, dubbing him: Fancy Fred, Five O'clock Fred, Flip-Flop Fred, McCain Fred, Moron Fred, Playboy Fred, Pro-Choice Fred, Son-of-a-Fred and Trial Lawyer Fred. [View an image of the Web site]
[...]
Nowhere on the site does it indicate who is responsible for it. But a series of inquiries leads directly to the website of Under the Power Lines, the political consulting firm of Warren Tompkins, Romney's lead consultant in South Carolina.
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Anti-Thompson site run by Romney donor