What is group x in /etc/group for and should I be a member?

A few days ago I noticed that suspend to RAM didn't work anymore on my T60 running sid. By chance I stumbled upon #484248 which explains that the user now has to be in the powerdev group to be able to suspend the machine.

If I hadn't found this information, I would have had no idea what to change to make me able to suspend my machine again.

Shouldn't we have a central list somewhere in /usr/share/doc explaining all the different groups and what they mean? Most of the times the package a group belongs to already explains what the meaning of this group is, but if you don't know the package, you're pretty much screwed.

I'm not saying, we already have too many groups, but a list with all the important groups and what they're for would be a huge usability improvement. We can't expect the user to find that information for every group alone.