Here is the "official" explanation from the Forum Suggestions & User Assistance Forum:

"The forums are now back online and should be working correctly for the most part.

There does appear to be some missing threads towards the end of the table which we are unable to recover due to the way it has repaired.

Whilst repairing the table the database server kernel paniced which corrupted the thread and user tables. The temporary data files were so corrupt that they infact were reading 16tb in disk usage(incorrect), we have recovered these and the only things that appear to be missing is some newer threads, instead of restoring a backup from yesterday this seems the best course of action to sustain.

However due to the consistant kernel panics the database server encounters we are deciding on what to do about it, we do however have the kernel panic and have repaired the main cause of that now.

Apologises for the extended downtime however we could not have prevented it.

-Scott"

Makes sense to me. My kernels are always panicing, and many politicians around here have corrupt stuff in their files.

Looks to me like a whole lot of threads are missing. But, I would guess that in 2 days we won't remember what they were or what was said.