Speaking as someone who maintains an ISP spam filter...
They're not clear in the article whether this is random email splattered out to any email address the senders can get their filthy fingers on, or messages sent to a list of people who have specifically requested mail.
For a filter system in general, the former are spam no matter who is sending them. The latter are not spam and must be allowed through.
HOWEVER.... The ultimate authority on what mail should and should not be allowed through to any given specific recipient is in fact that individual recipient. Any mail filtering system MUST include a method for the recipient to declare any arbitrary message spam or not spam, irrespective of the more global filter's results.
Biting the hand that feeds IT
