I am also looking forward for such kind of a mod with infact one more feature.....
The mod should be able limit the number of threads that a user opens in a forum for a given interval of time, which may be per hour or even per day.
Just found two such mods...
Maximum New Threads/Replies Per X hours Per Usergroup & Forum
Throttle Posts/Threads (restrict number of posts/threads per 24 hour period)
However the first one seems to be UnSupported now, and the second one doesnt have the feature of having such limit on a per forum basis.
Would appreciate if someone could script out such mod