Take a look at this letter to Dear Abby. In my opinion she completely misses the point and in doing so provides a great illustration of the importance of communication concepts in understanding a complex interaction. In this letter, a wife complains that her husband makes all the decisions about gifts and about how expensive they should be. In this case, he decided on a $100 bond for a grandchild. So, the wife correctly asks, shouldn't she have had some say? Btw, both husband and wife work full time or so it seems. But, Abby primarily addresses the content message--yes, Abby agrees, the bond is the better choice. It wasn't about the bond, Abby! And she misses the point because she doesn't see the difference between content and relationship messages. The content message was about the bond and that's the message that Abby addresses. But, the more important message was a relationship one that commented on their relationship in a way the wife found objectionable--he was the boss and he would make the decisions unilaterally.
Another way of looking at this is through the lens of equity--from what appears in the letter, I'd assume that both husband and wife contribute equally to the costs (they both work full time) but that the husband is deriving more of the rewards (making important decisions) with the result that resentment and relationship dissatisfaction develop.
I think this letter provides a useful way of showing students the value of seemingly academic (and therefore useless) terms in understanding everyday issues.