I don't know how accurate the graph may be, but I don't need a graph to tell you activity is dropping. I come here everyday and know first hand how slow it's gotten. It's dropped off quite a bit in terms of consistant activity over the past three months or so...
..and guests are not the same thing as members Andrew. Most those 'guests' are actually just bots crawling the site. They're not unique visitors, they're not members registering and staying on the site, so those stats don't mean much in terms of activity.