A self-justification Darby originally wrote for Breitbart's Big Government can be found at http://www.grouchyconservativepundits.com/index.php?topic=4367.0;wap2.
It runs through his claims of having had a run-in with ACORN in New Orleans after Katrina when he was still ostensibly a leftist, says that his growing disillusionment with the left after he returned to Texas led him to become an FBI informant, and ends by smearing activist Lisa Fithian.
And here's something from Matthew Vadum praising Darby and Stranahan. Vadum is the person who did more than anyone else to destroy ACORN and is the inventor of the complicated conspiracy theories involving people like Frances Fox Piven that Glenn Beck has been responsible for giving wider distribution. Beck has more or less said that Vadum taught him everything he knows.
A year ago, Vadum recommended the Darby/Stranahan radio show, writing, "Darby is the former radical community organizer who helped undermine an anarchist plot to attack the 2008 Republican convention in Minnesota as revealed in my book, Subversion Inc.: How Obamas ACORN Red Shirts are Still Terrorizing and Ripping Off American Taxpayers (WND Books)." (https://www.capitalresearch.org/2012/04/darbystranahan/)
So if Darby has been seen crawling around, this is not just some random FBI provocation. This is the usual suspects looking to paste the Trayvon Martin protests into their all-embracing conspiracy theories and using them to smear Occupy and/or the Democratic Party. (They don't much seem to care which.) The protesters are well-advised to be on their guard.