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.
Google's decision to shut down Reader's content-sharing features, announced last week, has led some users to in discussion forums and , and even set up a .
In addition to objecting to the requirement to give up pseudonyms -- especially in Iran -- in order to continue sharing, users also have complained about the loss of a dedicated place for RSS feed sharing.
In their view, it will be less convenient and less useful to have Reader content sharing reflected within Google+, along with a wide variety of other non-Reader content.
Sharing Reader content will now be based on Google's +1 button, which is tightly integrated with Google+, and on Google+ Circles, the feature that lets users organize their Google+ contacts into different groups, like family, co-workers and any other category they define.
In addition to the Google+ integration, the upgraded Reader includes a user interface redesign that is meant to be cleaner and simpler.
It's not clear whether users will be able to carry over to Google+ the social connections they have established using Reader's now retired "friending," "following" and "shared link" features, or whether they'll have to recreate them manually.
Google is making it possible for users who decide to stop using Reader to their account data.
"We hope you'll like the new Reader -- and Google+ -- as much as we do, but we understand that some of you may not. Retiring Reader's sharing features wasn't a decision that we made lightly, but in the end, it helps us focus on fewer areas, and build an even better experience across all of Google," wrote Alan Green, a software engineer, in .
People who haven't used the Reader social sharing features will feel no effect from the Google+ integration.