Mike Myers nailed it.  You cannot host a conversation, and then walk away without inspiring another conversation or continuing to add to the one you started. For example:

• "The radical reconstruction of the South after the Civil War was neither radical nor a reconstruction. Discuss."
• "The Holy Roman Empire was neither holy nor Roman nor an empire. Discuss." (This quote is based on a famous comment by Voltaire.)
• "The peanut is neither a pea nor a nut. Discuss."
• "Ralph Fiennes is spelled neither rafe nor fines. Discuss."
• "Duran Duran is neither a Duran nor a Duran. Discuss."
• "Rhode Island is neither a road nor is it an island. Discuss."
• "The Thighmaster is neither a thigh nor a master. Discuss."
• "The Progressive Era was neither progressive nor an era. Discuss."
• "Did Truman drop the bomb on the Japanese to end the war or to scare the hell out of the Russians? Discuss."
• "The Mormon Tabernacle Choir is neither Mormon nor a tabernacle nor a choir. Discuss."
• "The New Deal was neither new nor was it a deal. Discuss."
• "The Romanesque Church design was based on the Roman Basilica. Discuss."
• "The chickpea is neither a chick nor a pea. Discuss."

A good talk show host knows how to drive interest and engagement.  They bring you in and make you feel part of the experience.  They communicate closeness through the screen.  They bring interesting scripts, stories, objects, guests and acts.  They bring compelling social objects to the table for their character, guests, in-studio and at-home audiences to interact with.  They engineer relationships.  They earn trust. 

Social is like an always on talk show.  YOU need to keep it compelling, real and relatable, whether you're a brand marketer, an independent blogger, or a radio personality.

Keep it real.  And remember that it's ok to have Barba Streisand (or your CEO) stop by for a chat.  They make for remarkable social objects and personalities and they will delight their fans in so doing.

PS - Speaking of talk shows, what about Oprah? Whether or not she understood or really ever used twitter, Oprah built tremendous social equity, successfully socially engineered through broadcast media.  But there are very few Oprahs.