Update April 2, 2019: the links below are not working anymore.
Google Plus is a nice social platform with tens of millions participants. I found it especially nice for scientific posts, e.g. by John Baez, Moshe Vardi, or about symplectic geometry, about Majorana Fermions, and with a discussion about What is combinatorics. A few months ago Google announced that Google+ will be closed. This is going to happen today (March 31, 2019) in a few hours. For example, I am not even sure if the above valuable links will continue to operate. (Every individual user can get his own stuff.)
For possible answers on why Google shut down Google Plus see this Quora question.
My question is different. Is it legitimate for Google to close Google+? Is it legitimate and is it ethical for Google to eliminate existing content from the public domain?
Let me state clearly my opinion:
Google has strong ethical/moral obligation to maintain at least for several years public access to all Google+ existing material.
The fact that huge content that millions of people spent time and effort creating and that people spent time and effort to search and find, is deleted — by a huge and successful company — is very problematic
(Related post: What do firms want .)