Everybody knows somebody?

One of the most disheartening pieces of advice given to young Americans by ''realistic'' elders is that ''it's not what you know, it's whom you know.'' It is equally disheartening to have a high administration official now say that ''everybody knows somebody.''

To be sure, Charles Wick, head of the United States Information Agency, did know somebody - Ronald Reagan - before he got his own Washington job. And, in answer to recent allegations, he now admits a few people with family ties to the administration maybe did have an edge in getting jobs with his agency - without any improprieties.

True, as Mr. Wick suggests, qualified people should not be penalized because of family ties. But an appearance of favoritism among those already well off is not very encouraging to Americans outside the circles where ''everybody knows somebody.''