The same exact mechanism (and the parent already alluded to it in his comment: "Janette has the same problem while learning about X so she takes his code, makes a few changes and puts it on her blog").
Non experts look for tutorials,
They chance upon tutorials by non-experts
They don't know enough to tell they're junk
They use the code, link to, and suggest those tutorials to others
Those tutorials are getting higher ranks, attracting even more non-experts
Non experts look for tutorials,
They chance upon tutorials by non-experts
They don't know enough to tell they're junk
They use the code, link to, and suggest those tutorials to others
Those tutorials are getting higher ranks, attracting even more non-experts