Google announced in October 2018 that it would shut down the consumer version of Google+, the social network it had launched in 2011. The immediate cause of the announcement was the revelation that a software bug had exposed private profile data belonging to up to 500,000 users, and that Google had discovered the bug in March but had chosen not to disclose it publicly.
The decision not to disclose was made, according to reporting at the time, partly because there was no evidence the data had been accessed by outside parties, and partly because of concerns that disclosure would attract regulatory scrutiny and invite comparisons to the Cambridge Analytica situation that had dominated headlines earlier in the year. The logic was understandable. It was also the wrong call, and the announcement of the shutdown in the context of the disclosure made it considerably worse than a straightforward product retirement would have been.
Google+ itself had failed as a product years before the shutdown was announced. At its launch in 2011, it had genuine momentum. The Circles concept for organising contacts was more thoughtful than Facebook's friend model. The initial user experience was clean. Google pushed it aggressively, integrating it across its products and making it a requirement for certain services.
The problem was that the people Google wanted on Google+ were already on Facebook, and Facebook had their social graph, their photos, and their accumulated activity. Switching required not just changing your own behaviour but convincing everyone you wanted to stay in contact with to change theirs. That coordination problem is one of the hardest in product development, and Google did not solve it.
The more Google pushed integration with other products, requiring Google accounts and encouraging Google+ activity as conditions of using other services, the more it generated resentment rather than genuine engagement. Active users on Google+ tended to be enthusiasts rather than representative of the broader population Google wanted to attract.
What the Google+ story demonstrates is that network effects in social products are not just strong, they are directional. A social network without the people you actually want to connect with is not a social network you will use, regardless of its features. The product decisions that follow from not understanding that are usually more integration and more pressure, which make the problem worse rather than better.