Should the brushes be this bright on my vacuum cleaner's motor?
No, this is not normal. Some small arcing around the brushes is normal. In this case the rotor had segments that shorted resulting in very high current on the brushes for a percentage of the rotation. The higher current resulted in the larger arcs from the brushes since they take longer to extinguish. 

Not long after taking this photograph the motor began to smoke and smell horribly. So I disposed of it.