Facebook, Google, at al have to be ready to pull ads for, links to, and results containing blocked sites as well. They have to continue to monitor that over time as well.

I would imagine a two-phase approach: phase one would be the black-bar-type-doodle logo, phase two would be shutting things down. Whether phase two would happen would depend on how likely the bill is to pass, how well phase one went, and how much it would cost to police if it passed.