vBulletin offers admins and moderators two options when deleting a message. One can either delete it entirely, removing all evidence that it was ever there; or delete it "virtually", keeping the message and the information about it and just removing it from the forum list of messages.
I have been deleting spam entirely, but from now on will delete it virtually, leaving the evidence that it was there and that somebody removed it.
Readers are encouraged to visit
Home Base now to see how this works. The deleted messages are there, just "stumps" or "placemarkers" for the deleted items.
Notice that, out of the last 40 threads, 7 were spam. It wasn't always like this. It used to be worse. As Mags considered elsewhere, the addition of a "captcha" on the
register page - first in vBulletin 3.5 - cut down the amount of automated spamming. Each of these spammers has registered by hand, with a legal and operating email address. (Removing mail.ru from the list of permitted email addresses was once the fix to prevent as much as half of incoming spam. Most spammers are coming from old Europe and India.)