Viacom hasn’t been gentle with Google this year. In February they slammed Google/YouTube with a massive DMCA take down demand (and an equally massive press outreach). A month later they sued Google for a billion dollars. Between those two events they signed a content deal with Joost, a YouTube competitor in the professional content space. All of this seems to stem from the fact that Google promised Viacom a revenue share deal on YouTube, then failed to table a compelling offer.
Today Viacom snubs Google again, choosing to work with Yahoo on search advertising. There are few details of the deal, but it doesn’t appear that Yahoo is making any revenue guarantees, which are becoming standard in large search advertising deals. Google gave Fox certain guarantees in a $900 million deal announced last year, and Microsoft almost certainly guaranteed revenue to Facebook in order to get access to their search traffic.
In this case at least, YouTube appears to be a liability to Google, and Yahoo gets the benefit of being the next strongest player.