Regarding conversion rates, people have been trained to distrust email, but the same isn't necessarily true for blogs. If a spammer put together a well-worded "spam" message — especially if it's something people write about all of the time, like electronics, music or book reviews, etc. — it's not unreasonable to expect conversion rates would be much higher.
FWIW, anyone who hangs around blogs knows a spam comment when they see one. I'd imagine that it's even harder to make a fake blog post believable, since it's easier to wing something like: "yeah I agree [link to fishy site]" than it is to make a well-written post (especially if it needs to be generic enough to pass as legitimate in 12 million different blogs...)
