From the April 15 Cincinnati Enquirer article:

Fox News unexpectedly canceled conservative talk show host Sean Hannity's appearance Thursday night at the Cincinnati Tea Party Tax Day rally, leaving a lot of disappointed fans - and a lot of confusion.

Hannity was scheduled to hold a book-signing and a live taping of his talk show during the event.

Fox News Executive Vice President of Programming Bill Shine issued a statement to the media Thursday evening saying Fox had decided to call Hannity back to New York to do the show because officials believed the Tea Party was using Hannity to make a profit at the event.

“Fox News never agreed to allow the Cincinnati Tea Party organizer to use Sean Hannity's television program to profit from broadcasting his show from the event,” Shine said. “When senior executives in New York were made aware of this, we changed our plans for tonight's show.”

Criticism that the Tea Party and Hannity were trying to make a profit from the event began bouncing around on blogs, including the media blog Media Matters, about two days prior to Thursday's rally at the University of Cincinnati's Fifth Third Bank Arena.

“Unequivocally, from our standpoint, this is wrong,” Kevin Smith, president of the Society of Professional Journalists, told Media Matters. “For a news organization to charge people for access, then take that money and roll it over to a political action group that they cover quite a bit ... There is a clear conflict of interest here.”