It's a habit for me, bordering on a ritual, that whenever I ride I always tuck my pant cuffs into my socks and my laces into my shoes. I used to take my bicycle (my wonderful Bianchi) to work every day for what seems like ages. One fine day, the end of my crank caught my pant leg somehow (it unrolled a bit and I didn't stop to take care of it) and it fed it to my front sprockets right as I shifted the chain over it. Kissed those Bugle Boys goodbye. If that isn't enough for you: check how long your shoelaces are! On one of my Y-frames I was going downhill while pedaling to make extra time (running late, of course) and I felt my shoelace coming untied. I can only guess at the process, having something to do with the rear sprockets this time I believe, but my ankle was twisted as my shoe was yanked off. A prickley bush was kind enough to catch me. Dammed lace DID NOT break. Being late for work was the least of my problems.
These incidents occurred while on a pedalled bike. On a motorized bike, these issues become potentially life threatening!