Nielsen (NYSE:NLSN) has been asking Google (NASDAQ:GOOGL) to add tracking codes to YouTube videos for years, but Google has refused. Why wouldn't you just trust YouTube's own viewing numbers?

But Big G has finally come around to Nielsen's worldview, opening up YouTube videos and other Google-owned media to third-party eyeball tracking. Ad buyers want to know more than just how many video hits "Gangnam Style" has amassed (1.8 billion, for the record). In the following video, Fool analyst, former Nielsen worker, and all-around cool customer Anders Bylund explains why this is a big deal.