I get almost no SPAM in the first place, even with a freebie account (gmail, in my case). Some freebies are worse than others; Lycos sucked. Yahoo was bad for awhile but I eventually got it under control. I actually get less SPAM through Gmail than I do at my work account, which has a veritable obstacle course of firewalls and SPAM detection. I never open anything that isn't very obviously from someone I know, and I run anti-virus stuff regularly.   

And Rapaire is right; so many small businesses and nonprofits use it so much that having to pay for it would be a real kick in the teeth.