Neoneocon has some thoughts:
Barnett noticed—as many had, even at the time—the enormous difference in articulateness between Teleprompter-Obama and Obama unplugged (the latter is the title of Barnett’s article). That was the easy part. The more discriminating observation Barnett made was between the message of Teleprompter Obama and the message of ad-lib Obama. The two were not just different in degree—they were profoundly opposite in tone and essence. Ad-lib Obama was far more angry and more radical—indeed, although Barnett doesn’t mention it, this Obama resembled the angrier and more radical Michelle Obama, in her earlier campaign remarks that drew so much controversy.
Obama is addicted to his Teleprompter not only because he knows he sounds better—smoother and smarter—with it than without. The deeper reason for his reliance on it may just be that he differs so profoundly from the persona he wishes to convey that he quite literally cannot trust himself to speak without it. Shorn of the Teleprompter, he not only runs the risk of revealing a disfluency that could rival (or even exceed?) that of his reviled predecessor George Bush—he may reveal who he truly is, an angry man with a profoundly radical agenda for America.
No surprise to those of us who paid attention all last year.