Desktop search revenue is dropping this year, and mobile search revenue is jumping (-9.4% and +82.3% respectively). The price of mobile ads is far less than desktop ones. However, the growth of mobile is more than enough to counteract that and companies like Google (GOOG) are growing in due part to this. Google in particular is paying a lot of attention to mobile and aggressively developing it.
In my opinion, Google will profit, not be harmed, by the mobile trends. Google already has the biggest mobile user base in both search and operating system (Android). This means that Google always has a massive TAM (total addressable market) for maintaining and growing its revenue. It will find more and more ways to connect with users through new products and extensions of existing ones, in such a way that it leads them to profit. Overall, I think Google stands to benefit in the long-term from the shift to mobile, an area that it controls. Thus, among other reasons, I am a bull on the stock.
Hyperlink: http://bits.blogs.nytimes.com/2014/03/13/weakened-by-mobile-desktop-search-advertising-is-declining/
Disclosure: I am long GOOG.