Universal Music Group, Sony BMG Music Group and CBS have all teamed up with YouTube, in various deals. The partnerships are different for each company, but all have relatively the same goal of helping YouTube reach fully-legal status and compensating artists for their works, while at the same time increasing YouTube's ability to, of course, advertise. Sony and UMG's part in this will result in a permission-based viewing systems, whereas CBS's part will allow CBS themselves to dictate what content is put up and what type of advertising goes next to that particular file.
The Sony BMG deal will be similar to that with UMG, allowing both artist music and video content to be used with permission. YouTube's deal with CBS will allow users to purchase content such as news, sports and prime-time programming from its CBS brand television channels. It also includes technology that will allow CBS to find unauthorized CBS content on YouTube and remove it, or choose to keep the content up and stream advertising next to it.
A bit scary, if you ask me. This is all separate from YouTube's other goals, such as working with Google to potentially get online stores worked in with the site. Cooperating with giants like this will definitely help YouTube's chances of being purchased by a larger company, though either way the site will need to change dramatically.