I see a lot more young hipster riders around here who've converted old 80s bikes into fixies or single speeds. I am glad to see the trend to some degree, but their riding skills are almost universally horrible. I try to avoid them getting on my back wheel, and if I'm coming up on a stop sign I let them know in no uncertain terms that I am STOPPING.
I am more afraid when I am in my car, because they are so unpredictable when they make a complete mockery of traffic laws. I just try to drive more conservatively and keep my eyes peeled at all times.