Plus, how much direct effect do you think media coverage has on child abduction cases? I hardly think it would help, unless the investigators have a clue that could benefit from public information, and even in that case you get thousands of bogus leads. Trust me, I was in the DC Metro area during the whole Levy/Condit thing, and I didn't see the media coverage help at all. The police got thousands of bogus leads.
...and there were thousands of bogus leads during the sniper case, too. But because of the news coverage, eventually, the real leads came in. Without the news coverage, you think the truck driver would have had any chance of recognizing the vehicle? It only takes one good lead (amongst the thousands of bogus ones) to solve the case. Same for the kidnappings.
Otherwise, you have some valid points in the rest of your response... I'm not suggesting that the news media cover EVERY abduction/kidnapping, but I do think they're irresponsible in their choice of which ones to cover.