In my local riders forum we do something really simple that costs nothing but a couple minutes a day. Review every new member before allowing them to join. Takes 1 second per member. Is their name halfi828gskf? Membership denied. Sure, might take a day before your accepted to join the forums, but I think its worth it.
Give me the permissions to do so and I'll do it personally (if admins see this). All I do is sit and browse while at work all day so why not.