In just two week’s time, the concept of personal digital file cabinets has really gained ground. Late last night, San Francisco search company LookSmart announced that it has bought Furl.net.

You may not have heard of Furl; it’s been around less than a year and only has 16,000 registered users. But through a fair amount of buzz in the blogging world, it has helped reshape the idea of personal online bookmarking. Launched in January, Furl allows users to save bookmarks to a central location (not a new idea) and save an indexed copy of the page for later reference (new idea). The second part is key because web pages come and go or get trapped behind registration walls or in pay-only archives. But as long you save a copy of the page with Furl, you’ll always be able to access its content. It’s like having your own personal Internet Archive.

“When I was online, I had accepted the status quo, the idea that I would read something and then forget about it,” Furl founder Mike Giles tells us. ”And then I started thinking about what would happen if a filing cabinet went digital.”

Giles added a search function to his digital filing cabinet, and later the ability for users to share their archives with each other, and he was set.

After the official launch of Furl in January, Giles was immediately courted by unnanmed companies who saw the genius of his service. Imitators sprouted up. And over the past two weeks, Amazon’s A9 and Ask Jeeves both announced personal bookmark storage services (though neither allows users to save indexed copies of web pages, as Furl does).

In July, Giles finally decided to sell to LookSmart. LookSmart says Furl will remain independent for now. But the search company plans to make Furl more robust (it’s upped the storage quota for users to 5 gigabytes). And ads will begin to appear in the results when users search their archives. LookSmart is also hoping Furl will drive users to LookSmart.

LookSmart is a second-tier search company realtive to the Googles and Yahoos of the world, especially since it lost a critical contract to provide Microsoft’s MSN with directory listings. Nonetheless, LookSmart’s purchase of Furl further validates the digital filing cabinet concept.

“A lot of us in the industry recognized that Furl was something special as a way to crack the search nut differently,” said Kevin Krim, LookSmart’s vice president of web properties. “It’s really darn useful, so it attracts a loyal use base. It has amazing synergies with a number of our businesses.”