What the growing number of product placements shows is that television companies are having to change their business model to adapt to the growing competition from the internet and the development of technologies like the DVR.
Previously, TV did not have as much competition in the entertainment sector. In addition, people could only watch TV live unless they wanted to go to the trouble of using a VCR to tape a show. In those days, companies' business models could rely heavily on traditional ads to create revenue. Today, ads are less valuable because people can skip them on the DVRs and have more options for other things to do besides watching TV. Therefore, it is harder to make money by selling traditional ad space and firms have changed their business models to allow for making more money via product placements.