As we have been building school web sites over the years, a common feature request we received was: "I want people to be able to put content in one place on the web site, but only that place." Translated, this meant that they wanted to decentralize control of the web site, and allow people freedom within the areas where they are responsible.
So, for example, the Football coach can put anything she wants into the Football team section of the web site, but she cannot put anything into the any other place.
As Drupal has evolved over the years (for us, starting in 4.5) we solved this in many different ways. However, starting midway through D5, and with some consistency in D6, we began using Organic Groups as the tool to address this functional requirement. In D5 and D6, this involved overriding many OG features on a pretty regular basis, as the default settings provided options within the user interface (UI) that ranged from distracting to scary, depending on the end user and their privileges within the site.
For Drupal 7, Organic Groups was rewritten from the ground up. To understate things, this was an enormous undertaking. The lead developer on this is Amitai Burstein from Gizra, and on this rewrite, he nailed it. The rewrite makes smart use of entities in D7, and, last November, Amitai made the key decision to simplify Organic Groups by deprecating the OG Group entity. This change has many benefits, and one of the more immediately tangible benefits is that the views integration is now much cleaner, which simplifies the work of site builders. We had been working with OG in D7 for about a year when Amitai announced his proposed changes, and the direction he was talking about dovetailed pretty cleanly with our experiences up to that point. It's also worth noting that Amitai's approach to maintaining OG is pretty incredible; the work required for the initial rewrite of Organic Groups for Drupal 7 was considerable, and the rewrite for the 2.x branch was no small feat either. It would have been easy to stick with the original approach in the 7.x-1.x branch, but Amitai made the call to simplify Organic Groups to make it easier to use, and that's a great choice for all of us in the community.
In addition to sponsoring some of the original development, we have tried to be pretty active in the OG issue queue, helping with patches and testing as part of our ongoing work. We have been working with the 2.x branch of OG since late January, 2012, and it has been incredibly useful. In D5 and D6, delivering a site built on top of OG required putting a significant amount of work into UI tweaks. The core functionality of OG was (and remains) incredibly flexible, but the rewrite simplifies the process of delivering a site that has powerful and extensible community sections while being easy to use. From a site maintainer/builder perspective, one of the main improvements in the D7 version of OG is the ability to provide rights on a per-group basis.
Ongoing development and improvements are taking place in the 2.x branch; if you have been waiting to test this out, well, what are you waiting for? Grab a copy, and start testing, now! Yes now! What are you waiting for?
For more information and background on Organic Groups, check out Amitai going over some of the details from his DrupalCon Denver session: OG7 - Pride and Prejudice.