Fortunately, today, the forum has 98 merit sources in total (from the previous figure at 130) and the total sMerits allocation for each 30 days increase to 21671 (from the previous figure at 20895).
I think what happened is a modification of the algorithm for selecting Merit sources to be somewhat automated. @theymos calculated numbers based on spending during the last 6 months with the deletion of inactive sources and the distribution of sMerits to the rest of the sources.
However, if this would've caused you to have a source merit of less than 10, then you were removed as a merit source
In short, inactive sources were deleted and 8 new members added.