I'm currently registered for two races. The first is a marathon that I had to qualify for - even though only fairly fast runners can qualify for that one, the winners will be crossing the finish line while I am several miles away.
As of this morning, I am registered for another race that also attracts some of the fastest runners in the world. I didn't have to run fast to enter this one, but I did need to be fast - very fast - at registering. The online registration was open for just 3 minutes and 43 seconds before the race filled up!