Because we upgraded to a new more robust spam filter, I decided to remove Admin approval to see what happens.
Looks like we will need to go back to admin approval. That stinks because it means a new member/lurker can't just sign up and respond to a post. They have to sign up and wait for a mod to approve them, which can take hours to a few days depending on the time and how busy we are.
I can tolerate a little bit of spam if it means easier access to contributing on the forum, but I don't want it to ruin the board experience either. One bad account means it's not perfect, but i want to wait and see how bad it gets before I switch back.