The cameras began arriving over the weekend on the street in Waldorf, where Navy petty officer Robert Dean Stethem spent most of his childhood.

By Monday afternoon, as a Navy delegation dressed in starched, white uniforms came to tell the family officially that Stethem had been killed by Moslem terrorists aboard a hijacked airliner, a cluster of cameras filmed confirmation of news that the media had been reporting for almost a day.

"We've had so much coverage, we've had enough," Robert's mother, Mrs. Richard Stethem, sighed in a telephone interview yesterday afternoon. Although describing reporters encamped on her front driveway as being polite and in most cases sympathetic, she said it had still been a difficult way to learn about the family's tragedy aboard the Trans World Airways jet hijacked in Athens Friday.

"When you hear that it's your son from the media, before you hear it from the Department of Defense, it's unbelievable," she said.

As the nation's media scrambled to cover the story of Americans once again held hostage in the Middle East, journalists were constantly reminded of the last similar media event, the Iranian hostage crisis of 1979. In many cases, they reacted more quickly to this emergency, tried to tread more gently on the sensibilities of those involved and drew on skills and even the language from the 444-day Iranian crisis that dominated the news more than five years ago.

Steve Bell, on ABC's "Good Morning America," intoned somberly yesterday that this was "Day Five," echoing the daily count during the Iranian crisis when ABC did a nightly update called "The Iran Crisis: America Held Hostage." "Nightline," ABC's late night news show which continued after the Iran crisis ended, has dedicated all three of its shows to the hostage situation since this hijacking began.

The Chicago Sun-Times needed only to use "Day Five" in its headline Tuesday to recall the earlier vigil, and USA Today asked in its cover story, "Hell in Beirut: Is it Iran all over again?"

But the tidal wave of coverage for this hostage story has brought with it some new criticism of the media from a public that may not have the stomach for a gruesome rerun of the more than a year during which the nation focused on Americans in Iran.

"I've gotten a lot of calls, which never happened during the Iranian thing, from people complaining about the press coverage," said radio and television talk show host Larry King. "About 20 percent throw in the question about the possibility of whether we are endangering lives. Or, 'Why show the strike force in Cyprus preparing to go? Why are you badgering the president standing outside his helicopter?' . . . I was really surprised."

For reporters covering this story, part of their motivation for marathon coverage of the Beirut hostages was not to be caught off guard this time. The Iranian hostage story built more slowly, at least for television, several journalists recalled, and it was sustained by President Jimmy Carter, who made it a virtual obsession.

"Everyone hopped on this story with full force this time, because this time we had an institutional memory," said Sam Donaldson, ABC White House correspondent. "On Nov. 4, 1979, I was doing the Sunday show for ABC, and I led with this story, but it was only one story. That was it. It was not this immediate flexing of the entire networks' resources that we have seen this time."

Donaldson and other White House reporters said that they also expect their coverage to be different this time because they expect President Reagan to react differently. "The Reagan White House is making an effort in many ways to say this is business as usual, as opposed to Carter who made it a fetish early on," he said before last night's presidential news conference.

Others saw a rehashing of the old Iranian-crisis reactions in the media, the same phrases as an example of how the news business reacts almost automatically to the lure of such a mammoth story.

"It's the damnedest thing. It's like you're all geese, you get up to a new world every day," said Hodding Carter, who was State Department spokesman during the Iranian crisis. He said reporters seemed to have just awakened to the fact that there are other Americans who have been held hostage in Lebanon over the last year.

"But ultimately, the only real question is really not whether the press has learned any lessons," added Carter, who has been a media critic and Washington commentator for the Public Broadcasting Service. "The question is whether the government has learned any lessons. The reason you have not paid so much attention to those hostages we've had for a year is that the government has not paid much attention to them."

Another veteran of the Carter hostage crisis, former White House counsel Lloyd Cutler, said yesterday: "The purpose of this hijacking is to maximize attention to their grievance and to exact concessions and to use the news media, especially riveting the American public's attention on their television sets."

George Watson, Washington bureau chief of ABC News, denied on Metromedia's "Panorama" yesterday that television serves as the "megaphone for terrorism." Watson said that history is "replete with" examples of terrorism, long before television was invented.

Moreover, for this crisis, the Shiites have not seemed to use television as openly as the Iranians. Without the hourly news conferences from terrorists or government officials, the media, television especially, has been forced to fill vast expanses of time when nothing has changed. The result is to rely heavily on experts.

One such instant media star is Dr. Robert Kupperman, an expert on terrorism at Georgetown's Center for Strategic and International Studies, who said that he has done more than 50 interviews in recent days, dozens on camera. He said that although many media people are simply worried about how this story will affect their news budgets, "the more responsible people are more concerned, 'Are we creating problems? Are we adding to them?' "

Still, many reporters felt that the public's right to know the details of this event outweighs most squeamishness or reservations. The question of whether the media should show photos of Stethem's mutilated body, as Time and Newsweek magazines and The New York Post have done, among others, is not so controversial among most journalists as it may be for the public.

"I hate it, but I think you have to run it," Hodding Carter said. "It's a horrible reality that tells you what these hijackers are about."