I've been getting a lot of email since January about the statistical graphs, particularly the users-logged-in-over-the-last-60-days figure and the total signups. Fact is, that those parts of the statistical feeds from Linden Lab were frozen in January (around the 13th/14th of that month) and have not been updated since, though the data is still flowing for other parts of the feeds.
I've made some queries about it, but there has been no response. It's anyone's guess as to why the data is unavailable, especially as it happened shortly before an interview with Mark Kingdon, where he was talking about the quality and quantity of the available statistical data.
It's been more than three weeks of downtime on this data, so if it isn't an intentional outage, I guess it isn't a priority item to fix.