This is pretty sound and basic SEO if you want to spend your time making dozens of very basic wordpress blogs about particular topics to grab some easy money.
Nothing wrong with this if you have time on the weekends, heck this could even be a fulltime job as the income will slowly climb.
However, this 'trick' is quite old, but probably new to some people...
The motivation for the audience at 500 Startups is less "In your spare time, start blogging about [red men's shoes] and try to sell $0.50 a day of AdWords clicks about it" and more "As one thing in your marketing arsenal, create systems and processes to mass-produce quality content about the market addressed by your SaaS application, scaling your userbase from the few hundred people you had at launch to something closer to the 200,000 your friendly neighborhood bingo sideproject has, show your user adoption graph to investors, create lots of value, and ideally end up rich."
Nothing wrong with this if you have time on the weekends, heck this could even be a fulltime job as the income will slowly climb.
However, this 'trick' is quite old, but probably new to some people...