The incentives are different between spam comment blogs and e-mail spam. Spam primarily sells shitty stuff for unsophisticated people: if you're bright enough

The incentives are different between spam comment blogs and e-mail spam. Spam primarily sells shitty stuff for unsophisticated people: if you're bright enough to obfuscate your address, even with [AT] ... [DOT], chances to sell you herbal Viagra or to phish your SSN are very low, there's little point collecting your e-mail address. OTOH, when spammig your blog comments, the primary audiences are readers and bots, so your net-literacy isn't a disincentive to spam.