It seemed like a clever idea. This summer, a small Web company, Stamps.com, partnered with the U.S. Postal Service to let people put their own photos on 37-cent first-class stamps.

Cute babies. Precious pets. Proud papas. The plan was to give regular folks a novel way to send their party invitations, letters, and thank-you notes.

Except this is the online world, where good intentions are forever being hijacked. E-mail once seemed to be a convenient way to pass notes back and forth -- until spammers figured out how to commandeer the system to deliver loads of unsolicited advertising. Message boards for high-minded discourse? They're also a handy place to swap pornographic images.

And so it came to pass that Stamps.com Inc.'s experiment became the target of pranksters at a Web site called the Smoking Gun, which ordered images such as convicted spies Ethel and Julius Rosenberg, Monica Lewinsky's famously stained Gap dress and notorious war criminals.

In no time, Stamps.com began restricting what images were permissible. The company will now accept only "color images of children who appear to be age 12 or younger, pets and animals, business and charity logos, landscapes, wildlife and vehicles," according to a notice on the Stamps.com site.

The company's trial with the Postal Service is scheduled to end next week, and the Postal Service is not saying whether it will continue to program.

Santa Monica, Calif.-based Stamps.com is just about the last of the dot-com-era companies still trying to carve out a niche in the not-quite-proven business of selling postage on the Web. Company officials hoped that PhotoStamps might be the product that delivered the company into prosperity. More than a million stamps have been ordered since the service was launched Aug. 10, and the hype helped double Stamps.com's stock price, from $9 to nearly $18.

But the stock was crawling back toward the $13 mark yesterday, as analysts debated whether the program has a future. The U.S. Postal Service has not said whether it will continue the program or cancel it, and a spokesman for Stamps.com said in an e-mail that the company's chief executive was unavailable for comment yesterday.

"Everybody's in a dither over this -- what we've been saying all along is that this is a test that will conclude Sept. 30," said Gerry McKiernan, a spokesman for the Postal Service. "We'll look at it then."

McKiernan said the agency plans to consider the issue for 90 days before issuing a decision. He would not say what criteria the Postal Service would use in deciding whether to continue the program.

The U.S. Postal Service would not be the first to have a photo stamp program, if it allows PhotoStamps to continue. A few countries, including Canada, Ireland and Switzerland, have similar programs, according to McKiernan.

In an electronically connected world where people are moving toward e-mail and online bill payments, anything that drums up interest in old-fashioned "snail mail" could be taken as good news. A presidential commission's report last year forecast that the volume of mail the U.S. Postal Service handles every year will fall from 202.2 billion pieces in 2003 to 181.7 billion by 2017.

Those who follow the movements of the U.S. Postal Service said they don't know whether the PhotoStamps will be approved or not, but some weighed in, in favor of the stamps.

"I hope they don't chicken out because of the embarrassing stamps that were created by the Smoking Gun," said Michael Schreiber, editor of Linn's Stamp News. "I think it would be foolish for them not to continue this. These stamps do nothing but encourage people to use first-class mail."

Josh Rubin, a designer in New York, purchased PhotoStamps with pictures of his two Sealyham terriers, Otis and Logan. Rubin said he liked the stamps, but that they are -- at a price of 20 stamps for $16.99 -- probably too expensive for regular use.

"I think it's a great idea for special occasions, but it's about a dollar a stamp, so it's not for every day," he said.

Collectors have mixed opinions on the stamps, but some think any attention is good attention. "Stamp collectors are very divided about it," said Robert Lamb, executive director of the American Philatelic Society. "Some think it undermines the dignity of the hobby. We believe that, on balance, it's going to be beneficial to the hobby because it's going to build people's interest in stamps."

As for the Smoking Gun, a site that normally specializes in getting its hands on more titillating documents such as celebrity mug shots, editor William Bastone thinks the program may have a future.

"By all accounts, it seems the PhotoStamps idea has been popular with consumers," he said in an e-mail yesterday afternoon. "We trust that if the USPS allows it to continue, Stamps.com will make sure their screening process is a bit more robust."

Bastone said the stamps his outfit ordered are now filed away with all the other odd documents and photos that his Web site has amassed over the years, where they will remain, "unless, of course, the phone bill is due and we don't have a regular stamp handy."

Stamps.com chief executive Ken McBride thought family photos would be used to personalize postage stamps.The customized stamps program, which Stamps.com and the Postal Service say is a pilot that will end next week, also received orders using controversial historic figures and images such as Julius and Ethel Rosenberg and Monica Lewinsky's little blue dress. Stamps.com finally restricted orders to photos of children, animals, business and charity logos, landscapes and motor vehicles. Most customers used personal photos of pets and family members to personalize their postage stamps. More than a million stamps have been ordered since the program began on Aug. 10.