• by Mark Walsh  @markfwal, October 1, 2008

The social media company also launched a partner program with four Web publishers--the HowStuffWorks, Huffington Post, National Geographic and Rolling Stone--that will let users explore content via StumbleUpon without having to sign up.

Both moves are aimed at expanding StumbleUpon's Web presence with the goal of signing up new members after they've sampling the service. "This is about giving users the experience of 'Stumbling' and then getting them to register," said Michael Buhr, general manager of StumbleUpon.

Through the service, users indicate their interests across more than 500 categories such as food, politics, or music, download the application, and then click on the "Stumble" button in their toolbar to access it.

StumbleUpon crawls the Web, much like a search engine, retrieving content--from personal Web pages to videos to product information--that users then rate positively or negatively. The more feedback provided via the "thumbs up" or "thumbs down" icons, the more relevant the content served up.

The company also uses that information to better target advertising, along with other user data including age, gender and location. Ads take the form of sponsored Web pages that fit a given topic and appear less than 10 out of every 100 "Stumbles"--the service's equivalent of page views. Ads can also be rated.

Acquired last year by eBay, partly because of its rapid growth, StumbleUpon's user base has more than doubled in the last year to 6 million people generating more than 350 million Stumbles a month. Over the last year, however, traffic to the company's site has fallen by half to 675,000 as of August, according to comScore.

Earlier this month, tech blog TechCrunch also reported that eBay had hired Deutsche Bank to find a buyer for StumbleUpon. Buhr declined to comment on the unconfirmed report.

But he stressed that the key metrics for StumbleUpon are its registered users and page views within the application rather than unique visitors to its site. That's because the business model is built on selling targeted advertising to its audience of registered users.

Still, by opening up the service to non-members, the company expects to boost site traffic in hopes of converting more visitors into members. To that end, anyone will be able to select topics of interest and browse top-rated content on StumbleUpon through an interface that mimics the toolbar. If users want to save any pages they've Stumbled on, however, then they would have to register.

Under the new partner program, participating sites will feature a StumbleUpon widget that allows users to discover and rate articles or other content from within the properties. "StumbleUpon simply targets the publishers' content to more relevant users, increasing a user's activity on the site," said Buhr.

At the same time, the alliances are meant to entice more people to sign up for StumbleUpon's full service. The company plans to name additional high-level publishing partners in the coming months.