Can he possibly have gone through several years of undergraduate college without making some special women friends? Unlikely. At the very least the National Inquirer would have found their stories worth space and ink as it did for the story of John Edwards' girlfriend Rielle Hunter.
I am reminded of Sherlock Holmes' observation that the important fact was that the dog didn't bark. In this case, the important detail may be that no one has come forward to claim to have been Obama's college lover, or summer fling, or whatever. I don't know what this datum means, but it likely means something important.