Shift in web advertising
I just read this, and it made perfect sense to me - we are becoming immune to traditional web ads. 
I posted this article on Mashable's advertising, and how my brain very literally did not register even SEEING ads on their page (I know, I know ... but at least I'm honest). I attributed the dissociation to ad relevance. However, maybe the engagement in social media is eradicating traditional ads. Think about it, how many HOURS a day do you spend on Facebook? When was the last time you bought something from an ad on Facebook? What was the last ad you even remembered - is that even possible?
Just sayin ..