Is Amazon.com trying to be the new Facebook? You might think so after reading the e-commerce giant's new patent for a "social networking system."

The U.S. patent, granted June 15, "provides a mechanism for a user to selectively establish contact relationships or connections with other users" and "automatically notify users of personal information updates made by their respective contacts."

The patent's two inventors are Brian Robertson and Warren Adams. Those are names of the founders of PlanetAll, a networking service that Amazon acquired in 1998 and shuttered in 2000. (PlanetAll was a Boston-area startup that was created by a guy who wanted to keep in touch with his college friends. Sound familiar?)

Is Amazon now seeking to correct a missed opportunity?

Updated with comments from one of the inventors.

Here's the abstract from Amazon's new patent:

A networked computer system provides various services for assisting users in locating, and establishing contact relationships with, other users. For example, in one embodiment, users can identify other users based on their affiliations with particular schools or other organizations. The system also provides a mechanism for a user to selectively establish contact relationships or connections with other users, and to grant permissions for such other users to view personal information of the user. The system may also include features for enabling users to identify contacts of their respective contacts. In addition, the system may automatically notify users of personal information updates made by their respective contacts.

The patent was originally filed in May 2008, a decade after Amazon acquired PlanetAll and eight years after it closed down the service.

It's not clear if Robertson and Adams are still connected to Amazon. Brian Robertson is now CEO of Amonix, a solar power company in Seal Beach, Calif. Adams is listed as a partner at Vineyard Ventures in Edgartown, Mass. I've tried to reach both but haven't heard back yet.

Amazon, in a 1998 press release on the PlanetAll acquisition, described it as a "secure, free service to organize and automatically update information about friends, business associates, relatives, and alumni." Amazon CEO Jeff Bezos sang its praises at the time:

"PlanetAll is the most innovative use of the Internet I've seen," said Amazon.com founder and CEO Jeff Bezos. "It's simply a breakthrough in doing something as fundamental and important as staying in touch. The reason PlanetAll has over 1.5 million members -- and is growing even faster than the Internet -- is simple: it creates extraordinary value for its users. I believe PlanetAll will prove to be one of the most important online applications."

But within two years, Amazon had shut down the PlanetAll site, and folded its features into Amazon's Friends and Favorites technology.

PlanetAll had some Facebook-like origins. A 1998 PC World story details how Adams wanted a tool to keep connected to his friends from Colgate University in Hamilton, N.Y.

Update: I heard back from Brian Robertson, now CEO of a solar power company in California.

He confirmed the "social networking patent" originated with PlanetAll but said he believed the patent was first filed by Amazon in 2004.

Robertson expressed some regret about PlanetAll's fate, saying "It exhibited very similar growth curve as Facebook. These things need critical mass, if you don’t care for and nurture it, or take it away, it dies."

But Robertson said hindsight is 20/20 and he can't knock Amazon's decision to shutter PlanetAll back in 2000.

"The decisions where to allocate engineering resources at the time were probably the right ones. So I don’t think that any wrong decisions were made," he said.

Robertson said the internet has grown a lot since PlanetAll took a stab at social networking, and said digital photos, a key element of Facebook, are much more available now.

Asked what he thought Amazon will do with the social networking patent, Robertson said he didn't know, but said he thought Amazon should "enforce" it.

"Nearly every social networking site is violating the patent," Robertson said. "Amazon should get its value out of it. They paid something for it and they invested time over all these however many years to get it done. And none of these new companies thought it up. They took an idea that already existed and did it themselves."

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