Just playing devil's advocate here. I commuted to college on the subway every day. I was friendly with a few people but did not make any life long friends as I had to work 40 hours a week and take a subway 2 hours a day. I kept in touch with a few friends after graduating but after five or six years I had lost just about all touch. I wasn't a loner in school, just busy with not a lot of time for socializing. With the exception of a couple of linked-in or facebook friends from school, I doubt many people or teachers would remember me. I am about the same age as Obama which means all of my professors are retired with a lot of them probably dead now.
There was a newspaper article that had an interview with Obama’s roommate and another that interviewed one of his classmates and teacher. Columbia also wrote news articles touting him as an alumnus when Obama was elected U.S. Senator and President.
What you will find in his transcripts from Columbia that he was probably an average student not worthy of admittance to Harvard Law. Big deal. JFK had lousy grades at Harvard and was accepted to Standford law. John Kerry had lousy grades at Yale was accepted to B.C. law.
All in all I really don't care what someones grades were at age 19. I certainly did not have anything close to 4.0 in college and it hasn't limited my career or graduate school choice.
Maybe, maybe not. As I pointed out there were a couple of people who remembered Obama at Columbia. There was a U.S. congressman in my graduating class as well. I have run into him and talked to him recently at a couple of functions. I don't remember him at all in college and he did not remember me from college. We both had similar schedules in college. I'm just saying it is quite possible. I don't remember reading about President Reagan's classmates from Eureka College.