Frank Kern didn't make any money until he sold a product that lied and claimed he made $115k in the previous month (and got sued by the FTC).
I think most of these guys that start a blog do so with the best intentions. They start making a little cash and blog about their experience. These are the sort of blogs you want to find and read because they actually give out good, real info. (mGrunin's video blogs are a good example)
Then they get some traffic and their method dies and one day they find they're earning more from their blog than their method and become a 'guru blogger'. Their posts turn to what they ate today (with included photos) or "who can lose the most weight" competitions with other bloggers. They have a platform so they start monetizing it and it becomes one of their cash cows, where each 'review' or 'interview' is a thinly veiled attempt at getting some affiliate monies (eg. John Volk (Loved his latest "I'll show you how I finally made monies on my physical product" which was a promo for SpeedPPC), and Shoemoney)
Sometimes all their shit, including their affiliate campaigns, physical product and blog falls into a heap of shit and they have to start blogging again to try to pay the bills (Uberaffiliate)
