I rarely get any off .Mac. I have had my email address with them for almost 3 years. I get all my junk mail from my Cox account. Loads of it. Close to 50 a day. Credit cards, fake college degrees, home loans, you name it.
And I use .Mac for almost all my accounts online. Amazon, Gap, etc. I think is just a matter of when the spammers find an email address, your screwed because you are going to get slammed.
If you try to turn if off, it just seems to make it worse too. I have close to 15 rules in mail now to delete this junk. I like using the junk mail folder to seperate legitimate advertisements from my email and it is a pain to sort it from the crap. I.E., I have signed up for offers from Staples, OfficeDepot, Amazon, etc. I want those. I don't want to sift through 20-30 unwanted junk to get to them.
Rules are working pretty well though. I capture most of it now and move it to the Trash right away.
Back to the original topic, I am quite happy with .Mac. That account is virtually void of unwanted junk mail.