Google Reader users who want to continue sharing RSS feed content with others thus need to set up a membership in Google+, the company's new social networking site.

If they have been sharing on Reader using a pseudonym, they'll now have to switch to using their real name, which is required for a Google+ account. Google has said that it will allow pseudonyms on Google+ at some point, but hasn't said when nor how.

Reader becomes the latest Google application whose functionality has been changed -- either mandatorily or optionally -- by Google+, which the company is in the process of integrating with many other Google sites and applications.

For example, users of the Picasa photo service can continue using a pseudonym as long as they don't set up a Google+ account. If they do, they have to integrate it with their Picasa account, and replace their Picasa Web name with their Google+ identity.

Google is also giving Blogger publishers the option of replacing their Blogger user profile with their Google+ profile, but doing so, again, requires that publishers identify on Blogger using their Google+ real name.