Ouch indeed, that's a regular autobot army, ---- well their bots, and their automatic ;D.
I do wonder if some form of verrification would help. the monster breeder game at http://monbre.com/?ref=Vincent tells you to write the words I am not a bot into the box in joined up writing when you create an account, ---- or maybe you could direct people on the registration page to go somewhere else to find a verrification code, --- -such as having the register link on the forum as normal, but then a message telling people that the code is on the database entry for a given game, such as fartman or whackamole (a noteable one people would remember).
Obviously image verrification would be desasterous, ---- but if we're getting that! many spambots creating accounts, ---- well obviously something needs to be done.
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)