Guess it all depends on the fit of the jeans you wear. I've worn jeans for a few mileage runs, never had an issue. But my jeans aren't the skin-tight kind, more loose fitting.

For one MR I wore sneakers, but for my international trips in Dec, I wore my timberlands, and they worked well, especially since it was cold and messy in Germany.

I think dark clothes in general are good, it is more difficult to notice if they're dirty.