THEY monitor users? - "Retargeting has received some bad press in recent times, with users feeling they were being stalked or spammed with ads from sites they had visited before.
It is in our interest to only serve ads to those people who are most likely to buy. We monitor this process – anonymously – so that we stop serving ads to users who are clearly not in the market for the advertisers' products."
"Retargeting: what does it mean for marketers?"
Disclosure: Long LOOK and happy to be so, too...