I think this keeps coming up because n00bs tend to think the way to get faster is to ride as hard as possible every ride and record the average speed. Eventually that number will go up. Unfortunately, this doesn't work beyond the first year of riding. Note that most of the people posting "average speeds" or asking why "it's a big deal" are, in fact, n00bs. It's too bad so many are so unwilling to listen to more experienced riders.