[cmrdporcupine]

I'm sure there's a technical solution at the browser level -- a way to break cookie matchers. At least when I worked in retargeting, cookie matching was the secret sauce.

Preventing third party sources (images, scripts, "share buttons" etc.) from issuing or checking browser cookies might break a whole pile of useful things, but it'd make the world of retargeted ads dry up quickly.

[dreamfactored]

The freely available non-cookie fingerprinting libraries are incredibly effective now.