I've wondered: who actually buys drugs advertised in spam? Who'd trust criminals to provide medicine that you'd actually, y'know, put into your body? That question was the privilege of someone healthy and wealthy enough to afford whatever medicines doctors are telling him to ingest. But plenty of Americans want medicines that are, when produced to USA safety standards, too expensive for them. When they get email from a "Canadian" pharmacy offering better prices, of course they respond; they don't have other options. If they get sold some medicine from a bad batch, they're screwed—but maybe they were screwed anyhow.
Plenty of this crime has settled in Russia: it's a supportive environment with plentiful technical folks and bribe-able government officials. If you're a pharma-spammer in Russia, you just have to be able to bribe someone high up in the FSB and you can operate with impunity. Well, that's mostly true; but it gets complex. Spam Nation describes a period when two groups vied for control. Then, it wasn't enough to bribe an FSB bigwig—you had to make sure you were bribing a better-connected FSB bigwig than your competitor was bribing.