Another option we should explore is treating these folk like the feds dealt with organized crime. Rather than try to prove that high-up Mafia kingpins ordered murders etc., they went after them for tax evasion. The fact that they had little legitimate income and lived well set them up for that sort of prosecution.
In a similar fashion, we could go after these people for other activities linked to their desire to get our money. Much spam is also deceptive advertising, so attack them (i.e. morgage agents) through state regulators and professional societies. Sic the FDA on those selling drugs. Find their actual address and, through a cooperative fire inspector, shut them down for fire code violations.
In short, BE CREATIVE!
--Mike Perry, Seattle