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Robert Scoble has a video interview with Drew Lanham, Senior Vice President for Nexidia, a company that can match contextual ads, such as AdWords, with keywords from audio files of podcasts or videos.
How’d they do it? They match the phonetics of the audio to a database and display ads that match the phonetics.
Watch the video to see how it works.
I’m guessing this matches up perfectly with Google’s recently expressed thoughts on acquisition targets. 
