There is a difference between things that may affect me and things that are my business. Sometimes they are the same but most often, they are mutually exclusive.
If someone is driving at excessive speeds around me, it can affect me but only for a short time. Think about it. He wants to drive faster than me so within seconds, he is far enough away from me that I can safely avoid any craziness he causes. It isn't worth getting heated over. Its not "OK" in the sense that they could pose a threat to other drivers but its not my business to interfere because I'm not in law enforcement. To do so would make me a vigilante and, in my opinion, just as big of an a-hole as the speeder.