MAY 18: Among the big impediments stalling the dynamic video-on-demand advertising market has been the absence of a national footprint for the medium. While advertising buyers can take advantage of the capability across most Comcast markets, for example, it isn't possible to include key media markets like Los Angeles and New York City in an aggregated buy. That's about to change thanks to today's announcement that Time Warner Cable Media has joined Comcast Spotlight in selecting BlackArrow's VOD ad-routing and insertion platform to power its dynamic VOD business. The announcement, although light on timing and geography details, signals the cable industry's resolve to present a common platform to advertisers and agencies that want to take advantage of the viewer-targeting possibilties dynamic VOD insertion promises. With a presence in Los Angeles and NYC in particular, Time Warner Cable's ability to insert targeted ads into viewer-requested VOD streams could make the medium more appealing for national clients.