Please connect me if you find any issue about this document: arowser@gmail.com
Google have never officially released API documentation for Google Reader, so this information is unofficial and subject to change. Some resource about Google Reader api is available, but unfortunately a lot of the information in that document is outdated, so I trying to gather these info and update it.:
After Google Reader integrating with Google+, the ability to +1 a feed item (replacing "Like"),
with an option to then share it with your circles on Google+ (replacing "Share" and "Share with Note").
Google said they'll be turning off friending, following, shared items and comments in favor of similar Google+ functionality.
so you should not use these api again, even though these api still available now.
You still can like some article, but only you can see like tag, and you can't see other's like tag.