Folks:
Although our administrative controls have done a reasonable job of keeping spam out of the forums, we have been collecting a ridiculous (600-and-rapidly-growing) number of users that are obviously bots. To address this, we've enabled reCAPTCHA for user registration, and deleted any existing forum user accounts with zero posts. Apologies to any legitimate users who had their accounts deleted, this shouldn't happen again.
Cheers,
Tim