Imagine an Internet company, such as Yahoo, collecting personal information on its users and making that data available to other people and third party developers.

Now stop imagining. Yahoo on Friday kicked off its ambitious “Open Strategy,” part of which includes the first-time collection of personal data from across its many online properties.

The company says the information – who a user is, who that person knows and what that person does – is only collected when a person allows it to be shared. And it is not to be used for the behavioral targeting of advertising.

But the program will let data be seen by other people – your friends may have access to your movie and music ratings, for instance.

And third-party developers writing applications to work on Yahoo would be able to use the information in their programs. Yahoo also envisions allowing consumers to take their own data and copy it to other Web sites for convenience.

About 300 developers gathered Friday for the application-development Open Hack Day at Yahoo’s Sunnyvale campus got a glimpse of the new system. It will roll out broadly “very shortly” and gradually accumulate information from across Yahoo properties, said Cody Simms, senior director of product management. In the past, Yahoo has allowed a more limited amount of personal data to be collected separately by its properties.

For the program to succeed, it is important for Yahoo to be seen as a trusted collector of the data, said Simms. It will be interesting to see what online privacy advocates say.

By Mark Boslet, Editor at Large.