The Economist posted a very interesting piece last week that cleverly compared the four big consumer Internet technology companies — Google (NASDAQ:GOOG), Apple (NASDAQ:AAPL), Facebook (NASDAQ:FB) and Amazon (NASDAQ:AMZN) — to the warring factions in George R. R. Martin’s A Game of Thrones fantasy novels and TV series.

If you haven’t come across the article, it’s very clever, entertaining and worth a read. And if you happen to be a Google investor, you should definitely take note.

As the tech titans battle each other — along with former giants like Microsoft (NASDAQ:MSFT) — Google seems the least secure. The tech giant is under assault from multiple directions and multiple challengers … and its strategies for diversification are getting mixed results at best.

Search Trouble

Let’s start with search — Google’s original reason for existence. Advertising, which is tied to search, still makes up 96% of the company’s revenues. A disappointing quarter in October highlighted the pressure its search profits are under as the company struggles with mobile search advertising.

The demand for mobile ads may be on the rise, but its profitability is falling. The number of mobile ads Google served up rose 33% year-over-year, but the price paid by advertisers dropped 15%.

Plus, while Google has 55% of the mobile ad market, 95% of the mobile search ad market and 75% of the desktop search ad market, the competition is circling — as The Economist article points out. Apple is doing everything it can to take business away, for one. Its iOS platform — which is increasingly being purged of Google hooks — moves users away from Google for search, while Siri voice search technology is another attempt to steal some market share.

Social media companies are also a threat, although none have made a serious play to take on Google … yet. Consider these numbers:

• Google processes around 3 billion search queries per day.
• In 2011, Twitter was processing 1.6 billion search queries per day.
• Facebook CEO Mark Zuckerberg, quoted by The Verge, says Facebook is “getting in the order of a billion search queries per day, and we aren’t even trying.”

The potential threat to search advertising from social media sites is troubling. Of course, Google responded with Google Plus, which turned one-year old in the summer. While it hasn’t exactly had Zuckerberg and “friends” shaking in their boots, Google Plus has surpassed 400 million members, roughly 40% of Facebook’s membership. Google Plus users tend to be far less “engaged” on the platform than Facebook users, though.

And the social media threat is just the beginning. Microsoft’s Bing search engine remains in contention, accounting for 25% of all U.S. searches in September. Plus, there’s Amazon. According to a report by Forrester Research, 30% of consumers are now going straight to Amazon.com to search for products — either for purchase or research — instead of “Googling” them.

Attempts at Diversification

Of course, the company isn’t just sitting still while all this goes on. A need to diversify has clearly been driving Google in recent years. While Android is largely about protecting that search market share (by putting devices pre-loaded with Google’s search and related applications in consumers’ hands), there’s also revenue potential in smartphones and tablets. Google has chosen to sell its Nexus versions at or near cost, but Motorola smartphones command a premium.

The company has been relatively quiet since announcing its latest Nexus tablets and smartphone at the end of October, but a few days ago news did break that Google is buying Canadian online package locker startup Bufferbox — another signal that a move to take on Amazon’s online shopping empire may be in the works.

Google has already been testing same-day shipping for online shoppers in San Francisco and Bufferbox may be part of an effort to assemble the pieces needed to expand the program. The Economist suggests a much bigger acquisition — like UPS (NYSE:UPS), which is worth less than half Google’s $46.8 billion cash pile — might be needed if it truly wants to lock horns with Amazon, though.

The Bottom Line

All in all, is Google in trouble? Its last quarter did disappoint analysts and investors as a big revenue jump wasn’t enough to stop a 20% drop in income. Granted, one bad quarter isn’t a trend, but Google is under siege just as it is trying to figure out a mobile advertising market that so far has proven less profitable than desktop search. Expect Apple, Amazon, Facebook and others to keep testing Google even as it seeks to diversify by expanding into their turf.

Still, the search engine giant isn’t in immediate danger. If it comes to a war of attrition, that $46.8 billion war chest dwarfs Amazon’s $5.2 billion and Facebook’s $10.5 billion.

But the right combination of challenges could result in trouble — either through loss of market share or the company overextending itself in attempts to expand beyond search and advertising. The stumbles it’s experienced recently show the never-ending battle is taking a toll and the days of Google being invincible appear to be over.

As of this writing, Brad Moon did not hold a position in any of the aforementioned securities.