Hulu recently introduced Hulu Ad Swap which puts complete control in the hands of the user by enabling them to instantly swap out an ad they are watching for one that is more relevant.
To do that, they need to know where people are at a particular point in time and, more importantly, they need to know an ad for a discount or coupon will get to them instantly.
With on-demand access to over 18 million songs, Rdio connects people with music and makes it easy to search for and instantly play any song, album, artist, or playlist without ever hearing a single ad.