[brandnewlow]

This is why Facebook's new retargeting is pretty exciting (disclaimer, I'm a cofounder of a company in the space, http://perfectaudience.com)

Facebook has/had the same issue: huge audience and targeting that just didn't capture intent. By opening up inventory to folks that have that intent data, retargeting companies, Facebook's able to "sell umbrellas to people in the rain" to use the lingo of OP.

It's going to make a big difference for them in the longrun and we anticipate Twitter doing something similar in the near future.