Ninety-nine out of 100 people can't tell you what RSS (Really Simple

Syndication) stands for. And while some predict that RSS message feeds may soon topple e-mail, even the most liberal estimates suggest that no more than 5 percent of computer users have experimented with it. Yet many publishers of e-mail newsletters devote lots of energy to developing RSS feeds. What is all the fuss about?

-- The pros -- RSS has been around for a while, but recently it has made its mark as an alternative to e-mail newsletters. Users download a program to retrieve messages from companies that provide information "feeds." It's the basis for Web log technology, and it may one day give e-mail platforms substantial competition.

Here's why: The feeds enable pull instead of push technology, and are not intrusive. Users subscribe only to the messages they wish to receive. The feeds steer clear of e-mail blockers and filters that often prevent critical content from being delivered. Also, few media companies offering RSS feeds ask subscribers to share information about themselves (of course, this will likely change: few Web sites required user registration in the nascent days of the Internet).

The simple truth is that RSS technology has the potential to bypass inbox clutter, and companies want to be ready if it does. "Spam is killing e-mail as a communications channel," says Mark Fletcher, founder and CEO of Trustic, the parent company of news aggregator Bloglines. "People are suffering from information overload and they are starting to fear the e-mail inbox."

-- The cons -- RSS has its drawbacks as well. Senders of RSS feeds generally can't use images, sound or other rich media; a quick headline and blurb must suffice, with a link to more content on a Web site. "They can't control how the content is presented or how it commingles with other content," notes Peter Mesnik, co-founder and chief technology officer of e-marketing and analytics firm IMN. Similarly, RSS offers little in the way of customization. "It's one-size- fits-all, blasted to everyone," says EmailLabs CEO Dave Sousa.

There's little evidence suggesting that the feeds drive sales and bolster brands anywhere near as effectively as e-mail newsletters do. And while the feeds are trackable, no industry-standard metrics exist to gauge their reach and⁄or impact. When asked how many people are subscribed to his company's feeds, John Roberts, associate vice president of product development for news at CNET's News.com, concedes that he doesn't know. "We look at things in terms of how much traffic comes back to our site [from the feeds], and that's gone up every month," he says. "Would I love to be able to give figures that third parties would accept or understand? Of course I would.

But we're not there yet."

Pundits vary wildly in their estimates as to when RSS will truly become a mainstream communications tool. Guesses range anywhere from later this year to 2007 and beyond, but most believe it will get there eventually. "If you plot the amount of garbage e-mail, the breaking point is coming sooner than anybody thinks," Peterson argues. But Sousa, an interested party given his company's focus on e-mail marketing, cautions RSS boosters that e-mail shouldn't yet be counted out.