Assange entered the limelight in 2010 after WikiLeaks (founded in 2006) revealed confidential diplomatic correspondence belonging to over 200 U.S. embassies. The opinions and gossip from various foreign diplomats were, to put it mildly, controversial. WikiLeaks became the first independent entity to pose such an extreme threat to governmental privacy.
Assange quickly became one of the most simultaneously despised and beloved people in the world. He was even voted as the Reader's Choice for Time Magazine's Person of the Year. So of course, what better way to ride the crest of a wave of international notoriety than a talk show? Apparently, Assange plans to make his guests a mix of "iconoclasts, visionaries, and power insiders," all of whom will be subject to Assange "challeng[ing] them on their vision of world affairs." With such a confrontational format, and with Assange being who he is, he might have more difficulty securing guests than he would like.
Oprah may have left a power vacuum in the talk show arena, but that doesn't necessarily mean Assange will be able to fill it. He'll probably end up following in the hallowed footsteps of The Chris Isaak Show and The Sharon Osbourne Show. It'll be a crying shame, but he'll always have that internet start-up to fall back on. And also the sex crimes.