One time I saw a person signing up on the site I Moderate
Checked the IP & it was from a known spam IP
I banned them as they signed up
I usually edit their post & put "IMA spammer & will be banned" as soon as I see the post
One guy I even changed his avatar to
He went on & changed it to something else....I changed it back
I edited his posts & copied valid posts in without his links
He spent about 15-20 minutes on the site before he gave up/realized someone was messing with him