Most of the spammers seem to have a couple of characteristics:
1) "new" posters with low post counts
2) they use certain "key" words or phrases in the post title or body (apple, phone, viagra, golf, etc)
So...can the software be configured to block posts that meet the above criteria, i.e. (1) low post count (less than 5, or 10), and (2) contain certain "key" words or phrases in the title or body of the post? Blocked posts would have to be sorted by a moderator since some of them might be real bonsai posts (i.e. a new member trying to post a thread about apple bonsai would get flagged)...more work for moderators. There is no perfect solution to this annoying problem...