SPF (Sender Policy Framework) is a system for email intended to let recipients assert that the email most likely originated from the indicated sender. As of July 2004, over 20,000 domains had registered their use of SPF. However, a recent report from CipherTrust suggests that spammers are supporting SPF faster than legitimate e-mail senders, with 38 percent more spam messages registering SPF records than legitimate e-mail.
To be fair, the SPF developers predicted this case and they never claimed SPF would be the final solution to spam. It theoretically helps make whielists and blackslists based on senders more accurate and reliable, which is a big improvement.
I think the interesting thing is that it shows just how organized the SPAM terrorists are. The spammers can just do it and actually implement and deploy SPF, while those of us in legitimate organizations are still having meetings and working to get buy-in from our superiors.