I see hundreds of comment postings submitted to my blog each week, but fewer than 5% get posted because I moderate each comment. Look at these two examples and guess which one gets deleted and which one gets posted: 1) "Wow, you have a great blog, you're a genius, I'm telling my friends about your blog. My site on <link>penis enlargement</link> will really benefit from this information." 2) "Dofollow blog comment links are getting harder to find, but I still get some traffic to my <link>SEO consulting</link> site that make nofollow blogs worthwhile." I'm not making up or exaggerating the first one. Most of the comment submissions read a lot like it. Maybe some folks get benefit from it, but I don't see how it has any relevance that Google would recognize in the anchor text or the text around it. The funny thing is, my comment form says that all comments are moderated, relevant ones will go live and irrelevant ones won't. And yet, they still pour in that way. Maybe someone can help me understand if I'm missing something.
I always assume that type of junk comes from spamming programs. At one point last year I was seeing almost 50 spam posts a day about knock-off bags. Too funny!