Flickr, the photo-sharing service Yahoo bought this year, says it's figured out a search system that will lead to smarter image-surfing.

How so? Tour Flickr's library of tens of millions of photos using this new option -- start by clicking the "explore" link on the site's home page -- and you can get the idea. The system, which Flickr ( calls "interestingness," uses a formula to analyze user behavior and determine which photos people will find most interesting.

The result feels more like a journey through the Web than browsing photos.

Much in the way Google invented an algorithm to rank Web pages based partly on how many other sites linked to them, Flickr devised a formula that quantifies user behavior around each photo stored on its site: how many viewers clicked on a shot, how many clicked to the next shot in that series, how many looked at a photographer's other pictures, and so on.

The site crunches that data, along with the descriptive words people add to each photo, to figure out which it should present first when people search for a particular category or randomly browse.

"Flickr has a wealth of information about how people are reacting to photos," said Flickr co-founder Stewart Butterfield. "We see which ones they click on, which ones they make comments on, which ones they add to their favorites."

Flickr's formula factors in subtle factors, too, such as the relationship between who posted a photo and who commented on it. "If mom comments on your photo, it counts less than if a stranger did," Butterfield said.

The new image-ranking formula is being introduced in stages (for example, only some searches allow you to sort photos by their level of interest) and eventually will help generate all search results on Flickr, Butterfield said. The idea is to give people two ways of searching, by date or "interestingness," and let them toggle back and forth between them.

Flickr offers both premium and free accounts for sharing digital photos, and adds about 250,000 images daily. The site's popularity seems to lie in the creative ways users can organize and share photos, using free-form word "tags" they can make up and search for later.

Buyer, Be Wary

A new shopping site aims to help scaredy-cat shoppers who worry that the merchant taking their order behind that computer screen might actually be some teenage hooligan in a basement in Russia. The BuySafe Bonded Shopping Network, launched last week, brings together more than 1,000 Internet merchants who participate in a "bonded seller" program, underwritten by Liberty Mutual Insurance Co., that guarantees each transaction up to $25,000.

The shopping portal was created by BuySafe Inc. of Arlington, which offers a screening and certification service for small and medium-size merchants that sell on Internet auction sites such as eBay and For merchants that sign up and agree to pay a 1 percent commission on sales, BuySafe validates their identities, examines their finances, reviews their business history and monitors their transactions.

While BuySafe is only two years old, the company says it has obtained insurance licenses in all 50 states. It employs 35 people and has raised more than $16 million in venture capital.

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