Search engine giant Google has taken yet another step in its effort to monetize YouTube, the online video portal it acquired for $1.65 billion about two years ago. Now, YouTube users can click on advertisement links leading them to products offered for sale at online outlets like Apple’s iTunes store and Amazon.com. Here’s how it works: Say you’re watching a Feist music video and get the sudden urge to own the song. Beneath the usual rate and share options, you’ll find direct links to Amazon.com and iTunes where you can purchase a download.