Maybe Harvard and MIT won't let you go there after getting a degree at another institution. I know Harvard won't accept anyone with more than 60 hours to transfer, and you can't relinquish hours. This may be because they don't want people trying to get in after another degree and using 60 hours from their first toward a second, enabling them to get a Harvard degree with only 2 more years of work. I am speculating, but I am almost positive less prestigious institutions wil let you get a second degree there. Also, you can almost always go back and get a second degree from the school you went to originally, so if you are a Harvard alum you probably can get a second degree.