In the last few weeks several big Web and social networking players have released versions of "open" platforms that allow users to port their data and their connections between sites and between devices. Does this mark a major turning point for the advent of Web 2.0?Well, yes and no. As my colleague Alexander Wolfe points out, Google's Friend Connect, announced on Monday, is a way for Web publishers to add social features to sites without programming -- but it's also essentially a way for Google to compete with Facebook, MySpace, and Yahoo to maintain relationships with users no matter where they travel across the Web.

Yahoo is developing Yahoo Open, which combines a "unified social graph" that journeys with you to various Web sites, a new applications platform, and other tools to bring social networking tools to conventional Web 1.0 sites. Similarly, Facebook recently launched Facebook Connect, and MySpace has come out with "Data Availability."

All of these systems will bring greater facility to social networkers to connect with their friends and their "stuff" outside the bounds of existing social-networking sites. But they also are ways of strengthening the links between the provider and the user. "Make no mistake -- MySpace is still controlling this data, even as it gives users the ability to ship it across the Web," writes Stacey Higginbotham of GigaOm.

A Yahoo rep who prefers to remain anonymous because he's not authorized to explain company strategy used similar language in describing the company's new Open platform at the Internet Identity Workshop today: "All sudden Yahoo users go out on the Web and they remain Yahoo users."

While they're not truly "open," these moves are hardly surprising: you can't expect big Web companies to be devising ways to actually loosen their relationships with their users. As several attendees at the workshop pointed out, though, they raise questions about the relationship between data portability and digital identity -- questions that will not even trouble the heads of most users.

Do you want Google, for instance, collecting data about your beer pong pictures from spring break in order to target ads to you and your friends? (Kevin Marks, who heads the OpenSocial program at Google, assured the Internet Identity Workshop that Google's only interest is in increasing overall Web use and connectivity.)

"With Facebook Connect," says the Facebook Connect Web page, "users can bring their real identity information with them wherever they go on the Web, including: basic profile information, profile picture, name, friends, photos, events, groups, and more."

The question is quickly becoming, who determines what my "real identity information" consists of and how it gets used -- Facebook? Google? Yahoo? Or me?