While on the surface Google may appear as an unstoppable monolit, on closer look you can see they are rather vulnerable and stand in a rather shacky ground.
Google lacks focus
Google, like Samsung, seems to just like doing stuff because it can without an overeaching purpose in mind. It is the mentallity of just throwing stuff about hopping something eventually sticks. While all those projects they have running get them a lot fo headlines and news, next to none of them eventually lead to a solid, marketeable and profitable product. This is specially evident when it comes to their hardware.
No solid hardware base
While you may argue that Google is a services (and not a hardware) company, being just a service or a hardware company is no longer enough in the current landscape where things are shifting from a war of devices, to an ecosystems war which comprises three elements: hardware, software and services. Google is good on services and more or less good on software but when it comes to hardware they really fall flat.
The poor sales and small number of Nexus devices and Chrombooks, the failure of GoogleTV and the letargic development process of Glass have merely go on to show that either Google doesn't takes hardware seriously or they are just no good at it. Without a solid hardware foundation, Google has nothing for it's core bussiness to safely fall back on.
The Android (Samsung) problem
While Android indeed enjoys a majority marketshare this has done next to nothing to create brand awareness for Google and win them significant mindshare. All people see is Samsung, LG, HTC, etc, hardware brands that happend to run Android. With Android, Google also has the problem that it is open source and not only can it be forked (like Amazon did) but it can be completelly redesigned up to the point of OEMs including their own apps as replacements for the ones Google offers.
While you may argue that this is "the beauty of Android", in the current market where very much every company wants to build their own ecosystem, this doesn't do Google any good and as you can see with "Android Silver", they appear to be aware of the problem.
Google is at the mercy of it's competitors
Without a strong hardware base and the opensource and highly customiizable nature of Android, Google is practically at the mercy of OEMs and it's competitors and given how things are going with each company building it's own ecosystem, things aren't going to end well for them, specially when you consider the fact that they have been burning bridges left and right.
How so? You may ask, look at what happened with Google Maps on iOS. Sure, you may argue that Apple Maps are a mess and what not but the reality is that in a blink Google Maps loss nearly all it's iOS marketshare. With the exception of some, the typical IOS user is openning Apple Maps all the time and with more people updating their phones, the more people that just use Apple Maps.
Something similar can heppen if, for example, Yahoo convinces Apple to use them as the default search engine; or if they do the same with Firefox (or some other company with a search engine). Google easily loses a lot of markeshare in those cases.
In short, Google really doesn't have a solid foundation and is ill posiitoned to engage in the current ecosystems war.