The business models are finding themselves having to evolve almost as fast as the technologies they extract profit from. This may be causing problems: commercial pressures and entrepreneurial opportunities drive a significant amount of technical progress but legal (i.e. Intellectual Property rights) and business pressures simultaneously seek to reign in and control the advance (or at least the direction and formal, legal specification) of information and communication technologies.
There is a subtle dissonance between the drive to greater technological sophistication and the desire to control this process and its products. As with so many other things – the psychological desire for control here confronts the evolving complexity of the world and in this specific case the consumer appears to be the winner, to some extent.
The sheer massive commercial scale of the number of adverts being broadcast through YouTube would have to outweigh the need for longer adverts. Market coverage is very broad, all that they require is more creative, more engaging and short-format commercials. It will be interesting to see what direction this takes in regards to art direction, visual iconography and narrative construction. I predict that more hybrid advertising/information and news or entertainment formats will be the commercially-driven YouTube advertising success stories over mid to long-range time scales.