Half the time I join a group only to see that there haven't been any posts in its forum for weeks or months.
I usually have to leave one (or more) other groups just to get this information. If I could see just the date of the most recent activity in a group, I could make a better informed decision if I want to do the whole join/leave merry-go-round that goes with groups.
It can just be the date, I don't need to see exactly what the group is posting about.
In addition, if there was a date or summary of the most recent chat activity for that group, that would be even more useful information for me.