I wrote scripts for my blog and still receive spam, so it's not only standard software that's vulnerable - they definitely use some heuristics or otherwise analyze blogs manually, one by one. Also, I see poor English (I mean, very poor English, not like mine) in spam posts, which means it's been outsourced already.
I can see how the spamming part gets done, but how is he able to get payed without getting caught?
If I see a spam link, and follow it until I get to a viagra selling website, I should be able to find either the spammer himself or someone who pays the spammer. How can he remain anonymous?