OK, now you've reminded me, so I'm going to gripe about it!
Yesterday I rode up Ashland/Clark in Chicago. Busy street, lots of traffic of the car, pedestrian, and bike varieties. I'm fine on these streets. I feel like I can handle almost anything that comes, short of a car door opening right in front of me.
But someone riding directly at me in the bike lane? Twice I saw a cyclist coming straight at me and started waving my arm, pointing to the other side of the street. Yelled, "WRONG SIDE!" OMG. Scary. One lady just cruised right past me, veering out into (and against) traffic to get around me. The other guy rode up onto the sidewalk. In this part of town, the possibility is decent that you're dealing with someone who's mentally ill, or not from this country. But still. The wrong side of the street? There are bike lanes on both sides. I can't imagine making the decision to ride down the wrong side.