I didn't think I had the competitive biking bug until I did my first "bike tour."
Normally, I don't bike with others and I rarely see any other bikes on my commute, but when I did this tour with all of these other bikers with their fancy-dancy bikes, it just came out. It drove me nuts to be passed left and right by others. I dropped the hammer the last 2/3s of the tour and held my position. When I came to pass someone, I played it off all cool, but the inner beast was chanting "THIS.... IS... SPARTA!"