I think it's pretty daft for this not to be in the core. Each forum has an option as to whether posts made in it should be counted toward user totals.
Let's say I go and reclassify some forums, lets say the staff areas, and decide posts there should not count towards totals.... I should be able to rebuild those counters without having to rely on a third party SQL query! To do so is just nuts imo. Credit to Jake for writing the query, but it needs to be amongst the built in counters and cache tools.