Why is guerilla marketing taking over social sites? For two good reasons: the environment and psychology align with guerilla tactics.
Social sites provide a perfect environment for marketers to directly focus ads to individuals. Technology is now available to track consumer purchases over the web and user profiles provide specific demographic information.
Of course, if you don't know that you are seeing an ad it's easier to pay attention. Companies recognize this and are posting their own YouTube videos cleverly disguised as product promotion.
To me this seems like a trend. As with anything in life you either take it or leave it. The more annoyed the public gets with seeing the same tactic over and over the less likely companies will use that technique. What really matters is the effectiveness of the ad. Does the YouTube video from Rayban make you want to buy their glasses subliminally? Who's really being fooled?