Activations can already be done at the new Yahoo Profiles site and with a beta of Yahoo Messenger 9 that was just released. Activations will be rolled out more widely in a few months when the option is presented to people when they log into their Yahoo Mail accounts, and at other Yahoo services after that.

Each new application will have to warn users about the data it plans to access, such as their address book, inbox or profile, and about who the information will be shared with. Patel admitted that this is a delicate area. Yahoo will make certain selections by default that users can then alter.

"Choosing the right defaults so people don't inadvertently give away their privacy is part of the challenge," Patel said.

The OAuth protocol allows users to give a site access to their data for a limited time, such as two weeks, said Neal Sample, a Yahoo chief architect.

Yahoo doesn't expect the Profiles page to become a major destination. Instead, users will eventually be able to install applications and display updates at their My Yahoo page, in Yahoo Mail, and possibly at Yahoo's main home page.