I also drew up the following 3 charts using the same data showing weekly activity for 1on1, 2on2, 4on4 from February last year through to September 2010. This was just to give a general trend over the full period since the site went active.
The figures are well down for FFA as well. Interestingly there is less peaks and troughs with FFA, with no real summer break however there has been a noticeable decline in numbers since 2009.It should be noted that while there are bugs in the way the info is sometimes displayed on the actual stats site, the query results shown here themselves were performed on the match data directly and should be fairly accurate.
Also the detailed figures are available if anyone is interested.