It's amazing to see the takeoff of banner ad "re-targeting", currently at Live Chat Concepts we dont use re-targeting but in my own personal browsing etc i see it's use everywhere.
In case you haven't noticed "banner re-targeting" is where you might browse Amazon or Best Buy for a particular item, then at a later date when you are browsing the NY Times you might see a Best Buy banner advertising that exact same item you were just browsing for 3 days ago.
For example i'm about to replace my computers keyboard. For a particular reason I'm after a keyboard from Logitech called the G11 that hasn't been made by them for the last 2 years. It took a while to find a retailer who had a new one in stock (hong kong) so i had to visit a lot of companies with Logitech keyboards (current model is G15 and G19) so about 1/20 banner ads i see at the moment is an ad for Logitech keyboards due to re-targeting.
Whats really interesting is that they aren't necessarily ads from the same websites i visited - makes me wonder what else they are sharing between each other.