It's really sad that nobody uses the groups feature on the website. It's one of those things that you would expect everyone to do, but it turns out there are only about 20 active people. If you want to organize brony meetups, have an internet band, group write a fiction, plot evil stuff, or anything that you can think of, you should really join or make some groups.
I still use them but just wait for a time when it is appropriate for me to post. I agree with you though.
I've joined quite a few groups. Although the only active one was the EP review team. Now it seems to have died down a bit. But I agree with Eight Star, that how most people see it.
I say I'm guilty. I joined few groups, but simply forget about them most of the time. from now on, I'll check on them from time to time.
I'm taking some time off from my staff duties for personal reasons, so that's why I'm quiet in the Review Team. I do agree however, there is a lot of untapped potential in Groups.