I've done the math. I don't own my own domain, and a lot of people who don't use SPF would still get it. Indeed, PANIX appears to use SPF, and I still got the email from other people.

You can stop berating me now: I wasn't complaining before: I was just noting that spammers forge From: addresses. They'll still be able to forge it, and I'll still get the email, and it doesn't really bother me that much.