Yahoo recently -- and rather abruptly -- revealed its plans to erase the majority of Yahoo Groups, and with it, a significant amount of the old web. According to archivists, some of it may be preserved by the Internet Archive. However, it's hard to not see this as the death knell for Groups.
Although, in a statement to The Verge, Yahoo claims it will listen to feedback in order to keep users happy.
We are tailoring Groups’ features to match the preferences of our Groups members. Most of our members connect and share content primarily over email, so we believe this change will streamline and improve the Groups experience. Yahoo Groups will continue to provide a way for people to connect with their communities around shared interests, and we will continue to listen to feedback to ensure we keep our users happy.
Once upon a time,Yahoo Groups wasn't unlike today's Reddit, serving as a hub for discussion on niche topics. While users won't be able to post to Groups anymore after December 14, Yahoo's statement seems to suggest that at some point, Groups could regain that functionality.
In the meantime, communication in Groups will be limited to email.