Interesting article by Diane Mermigas at Seeking Alpha about the challenges Google is facing as it diversifies into more and more areas, and it rumbles over the line dividing plucky upstart to hated giant monopolist:
Like past monoliths of new growth industries, Google appears to be invincible. But Google is vulnerable just because it is thinly spread in a rapidly changing marketplace where rivals are eating away at the edges and fighting for turf. A major shift in technology or consumer behavior could alter the playing field, just as it once did for broadcast TV networks, music companies, telephone companies and typewriter manufacturers.
Google is locked in its fiercest battles over search, email, office applications, social networking, portals and brand advertising, Web browsers, mobile operating systems, ad servers and exchanges, and operating systems.
Mermigas goes on to list a number of other challenges including: real-time social search, Microsoft/Yahoo search and advertising, digital books, streaming video and video search, mobile search and mobile applications and advertising.