I know the feeling. I've got several pairs of pants that have legs that are conspicuously cut off or sewn back together from when they've been sucked into the drivetrain. You're riding a long, feel a little tug on your leg, hear a horrific tearing noise, and think about how you should've stopped to roll them up better but were in a hurry. I once had a stray shoelace wrap itself around the pedal spindle as I was spinning down a hill at a good clip; by the time I came to a stop, Mr. Chuck Taylor had half his eyelets torn out and I felt lucky that my ankle was still okay.

Your drivetrain gets hungry sometimes, so roll 'em up or cut 'em off. It makes for a good way to identify other bike people, too.