In my community, the bike lanes are marked on the side of the road. Part of this marking for the bike lane includes an arrow that shows the direction you should be riding. However, I always see riders going the wrong direction. I haven't come across a rider going in the wrong direction yet while I've been on my bike, however, I have already decided how I will handle this situation. I will be yelling at the top of my lungs, "YOU'RE GOING THE WRONG WAY!!!" all the while building up my speed and heading right at the guy. They have 3 choices:
1. move off the bike lane to the left and let me go through
2. move out of the bike lane into on coming traffic
3. hold their ground and prepare for impact.
I think riders should realize it's just as dangerous to be going the wrong way on your bicycle as is to be on the wrong side of the road in your car.
The only exception that I'll make is to teens or children. However, I've let many young people know that they are not riding on the right side of the road. If you're an adult, old enough to have a driver's license, I expect that you should know which side of the road you should be on.