After long, careful consideration by the staff, we have decided to disable the option for Social Groups on these forums.
The main reasoning behind this is, because of the way the moderation for them was set up, they were very difficult to moderate and did not receive much attention. As such, many groups were spammy, repetitive, or otherwise breaking the rules, and it was too difficult to keep up with removing them all.
The vast majority of Social Groups that actually followed the rules can be slightly tweaked and posted in the Clubs, Clans, Games, and other Forums (provided there is not already a very similar thread there).
We are making plans to make up for this loss in forum functions, but it is unlikely that Social Groups will ever return unless there are significant updates in the moderation options.
How to find your group through Google Cache
The url for Social Groups is:
Put this url into google and you'l end up with the search results. Next to the title will be the word Cached. This is a recording made by google of the page at a previous date.
Click on Cached and the original page will open. You wont be able to browse, but you will be able to copy the links of each page. Put the link back into google and click Cached on the first hit on the results. Keep doing this and you'll be able to dig your way through the cached pages to find your original groups. You wont be able to search, so you'll have to do it manually. If you have the original link for your group, such as in your favourites menu, then you can just put it straight into google.
Please note that it will not always work. Sometimes it wont go back far enough, or the page just wont be stored in the cache. But using this method you should be able to get at least some of your information back.
But I recommend you do it NOW, before the cache is set to the current state of the groups being gone.