an advertising question

So you know the ads they show behind the catcher during baseball games? The ones that are composited on top of the green screen?  I’m curious…

  • Do the networks composite in different ads for different markets?
  • Even if they don’t (let’s say the economics are better for a national campaign), does the technology exist to do that?
  • When the game’s repackaged and sold on DVD, are new ads composited in?

I’ve heard of certain television series’ using chroma key technology to enhance product placement opportunities; I’m wondering if/how this type of technology is being used (in real time or not) to deliver optimized place- or time-shifted advertising.

Anyone have any experience here?