You can stop arguing over Meng Wong's SPF and Microsoft's attempts to use it as a Trojan Horse for its licensing schemes.

It's already broken.

Ciphertrust surveyed e-mail from May-August and its conclusion is conclusive:

It found that 34% more spam is passing SPF checks than legitimate e-mail.

Now SPF isn't totally useless. The system does protect against address spoofing and its nasty cousin phishing.

But it's still not a solution to the underlying problem. So try again.