All forums will get spam, even the ones which need admin approval before allowing someone to post can't filter out all spammers. Unless your meaning stuff which may get auto deleted before ever making it onto the forum, (like a 'denial of service' attack).
One thing I have wondered is. Do you (and all admin) get notification when we press 'report to moderator' I know myself and Don do (and I assume John does as well). All of us hit the report button (when possible) before deleting the post. I only ask as in recent times I stopped sending yourself a PM whenever someone needs deleting, unless they post a lot of spam all at once. there are currently around 10 to 12 people who required deleting from the forum. With 'LeroyEdiGh' being a particular pain.
Oh. in case anyone is interested, we have had 18 reported since beginning of November, and 190 reported this year, (with probably around another 25 deleted without being reported).