Spammer Question

[carllaponte]

In March my forum started to get flooded with spammers. These spammers were able to get set up as members and then start spamming. The moderators would then re act to the spam and ban the spammer and delete the posts. This went on from March thru last week when I became owner of the Forum. I'm not sure when the software was updated last but when the transfer was done last week my forum was updated to vbulletin 4.2.1. This update stopped new spammers getting accounts set-up. Currently we are only getting a few spams a day now by members that got in before update was done. Here's my question:

1.Is there any reason not to completely delete the spammers that are currently banned users? (aprox 15,000)

Thanks for the help!