Facebook users don't have ad blindness. I run Facebook ads with CTR as high as 3%.
Don't forget: The same people performing a Google Search also use Facebook, and they are in "buying mode" rather they are on Facebook or Searching.
Facebook strategy is re-targeting. They rolled it out a few months ago. If they use Retargeting + Ad Network, Advertiser can reach them on the content site after the search "our sites" and re-target them while on Facebook "or another site they visit in Facebooks' content network.
The true beauty would be reaching them on Facebook where they stay logged in, after they show interest in a purchase "beating them to Google", and being able to track that purchase to a specific user online or in-store.