Hello, I started my mileage/segment run career in college as well, but have not stopped yet. I use it to maintain my elite status, to get extra miles, and it can be interesting people watching. Though it can also be very tiring. A couple of favorites from 1999:
CO BOS-EWR-DTW-CLE-ATL (for about $65 each way!)
NW: BOS-DTW-ORD-MSP-DFW.
I like the idea of a video trip report...which I have not read yet, but somebody posted it. Might be interesting to do a trip report, say, with a mini disk recorder as well.
I don't think I could stand an international mileage run in coach...usually I upgrade my domestic mileage runs.
Agents have told me it is at least somewhat common as year ends. Also years ago on US:
BOS-LGA-DCA-PIT-CLE or variations of that.