Etiquette: Job Seekers need to reply to emails if they want respect (this goes for employer too)

A parent recently made contact with a person on the Resume / CV list. This is the parents explanation... "We emailed and then I sent my job description as she asked – with no reply.  Weeks have passed now and she did not have the common decency to get back to me."  

It is common courtesy to reply to future employers when they might send out their job description even if they do not think the position is right for them.  There is nothing more frustrating when you have a few people that you are contacting and trying to keep track of all the communication is hard enough without some of them not even replying to you.