Twitter fulfilled that underserved need that Facebook hasn't been able to, because until now Facebook hasn't made it possible for its members to share their profile content, with the exception of bare-bones information in public search engines.

Facebook has been taking steps to give members more options to share their profile content more widely in recent months, including the start last week of a test for a new version of its Publisher, the tool that members can use to post notes, status updates, links, photos, videos and other content on their profile "wall" and share them with their friends.

This new Publisher version, now in limited beta, lets members determine the privacy settings of each individual post they make, and includes the option for members to share whatever they post with "Everyone" on the Internet, on or off Facebook.

In March, Facebook started giving members the option to share all or some parts of their profile with everyone on Facebook; previously, people could only do that with hand-picked "friends" or members of the same geographical, school or employer networks.

It's not a simple task for Facebook to modify its site to match up with Twitter in the area of real-time, public postings, IDC's Dangson said. "Facebook's culture is different from Twitter's. Facebook is more closed because there you have a more robust profile," she said. Since people post more content on Facebook, the stakes are much higher in terms of controlling access to that content, Dangson said.

It will also be important for Facebook to clearly explain how these changes impact the way in which third-party applications apply privacy controls to the members' information they access, Dangson said.

Asked for comment about how the new privacy changes will be reflected in third-party applications, a Facebook spokeswoman said via e-mail: "Currently, when a user publishes a story through the Publisher for a third party application, they do not have specific per-post privacy settings. This is something we’re considering for the future, but developers currently do not have to 're-configure' their applications to accommodate these new settings. Additionally, nothing is changing with application privacy settings."

Dangson recognizes that the new per-post privacy settings would be difficult to require from third-party Facebook application developers, but said Facebook should strive to make the experience within those external applications as consistent with its main platform as possible.

"Unfortunately, consumers think of all activity within the Facebook platform as Facebook. If something goes awry with an application or consumers get confused about the different privacy standards, Facebook will take the blame," Dangson said.