If you take summer coursework at your own university, or one of comparable difficulty, does not matter. Even if you take them at a less prestigious university, and it is only one or two courses over your college career, does not matter. If someone took a good number of courses at a much less competitive school, I would certainly look for a reason (ie living at home to attend to a family emergency, financial need to take some credits somewhere less expensive). Summer courses can certainly be very challenging given the compressed nature, especially if one is keeping active in research, and/or with EC's. But they also can be very rewarding in that many times, the small class size promotes more interaction with professors and other students.
