I encountered some fool jogging in the bike lane recently, where there was an huge empty sidewalk. This was on a descent where I am normally doing 30mph. The bike lane was easily wide enough for the both of us, but the fool was in the left half of it, and I didn't want to take my chances passing him on the right and getting caught between him and the curb if he veered toward it, since the fool had his back to me. So I passed him while on the white line dividing a 4-lane street from a 5-foot-wide bike lane, then listened to him screaming and ranting at me after I passed.

And just for the record, I have been alternating my workouts between cycling and jogging, and I use sidewalks for running.