(NASDAQ:AMZN) and Google (NASDAQ:GOOG) (NASDAQ:GOOGL) are the business version of frenemies.

Though the two companies have not resorted to acting like the best of pals in public while saying means things about each other behind closed doors, they do have an increasingly complicated relationship in which they work together in some areas and aggressively compete in others. It's the same type of relationship that Apple (NASDAQ:AAPL) and Google have had over the years, which blew up in 2012 when Apple dropped Google Maps from its tablets and phones. That move backfired, since Apple's own map application was not up to snuff and the company had to come crawling back to its spurned partner.  

Amazon and Google have not had a major public falling out, but they are both moving aggressively into areas that are the other's bread-and-butter business. That could at some point cause the two companies to stop doing business with each other. This would hurt Amazon more than it would Google, but the two are better off continuing to work together. 

How are the two frenemies competing?
Google recently launched Google Shopping Express, which facilitates retailers' effort to compete with Amazon. The service, which so far is only available in a few markets, partners with major retail brands to offer same-day delivery on groceries, health and beauty supplies, home goods, baby stuff, and more. Shopping Express is even partnered with Barnes & Noble  (NYSE:BKS), so it can offer books as well, which is, of course, where Amazon got its start. 

Google Shopping Express is a threat to the largest piece of Amazon's business: retail sales. In 2013, $48 billion of the company's $77 billion in total sales came from "electronics and other general merchandise," while $21 billion came from media. Both are retail businesses. A portion of the media segment is delivered digitally, so it would not be affected by Shopping Express, but even just the first category is more than half of Amazon's total business.

Meanwhile, Amazon is making moves to hit Google in its biggest source of revenue. Though the company has not made a formal announcement, multiple news reports state that Amazon is working on an ad platform that would rival Google's AdWords, attempting to take a share of the company's advertising business that brought in $55 billion last year. The ad system would leverage Amazon's customer shopping data, giving it a tactical way to compete with Google's years of data, VentureBeat reported.

Google wants a piece of Amazon's core business and Amazon wants a piece of Google's core business.

How are Amazon and Google in business together?
Amazon and Google have what must be seen as a mutually beneficial advertising relationship in which the online retailer pays for traffic that translates into customers and sales. Amazon, as you can see on the  chart below from, is actually Google's biggest customer when it comes to search ads.

Chart via Statista

While losing your top customer is never a good thing, the impact on the search giant's ad sales from losing Amazon as a customer would be less than 0.3% of the total. 

Amazon, were it to stop spending money with Google, or if the search company stopped accepting its ads, would likely be hurt because nearly 20% of its traffic comes from Google, according to Alexa, which tracks and ranks websites. That's more than the next four sites that Alexa lists combined. Those four -- Facebook, Yahoo!, eBay and YouTube -- only account for 10.9% of the site's unique traffic. Some of that traffic from Google comes from organic search, not paid ads, but any rupturing of the partnership with Google would likely produce a severe traffic loss for Amazon.

Google also places ads on Amazon through its AdWords program. That is likely to be one of the first casualties if Amazon launches its own ad network, which it is reportedly calling "Amazon Sponsored Links." That would give Google one less place to put its ads, but it's hard to believe the change would have a material impact on either company. Google has countless ad partners, and advertising is such as small part of Amazon's business that it's not even broken out in the company's annual report.  

Both are better together for now
In the long run, Amazon's ad network could cut into Google's business and/or the search giant's retail efforts might take significant sales from Amazon. That's not happening yet, and both companies are better off pretending to be friends.

Google could lose Amazon as a place for AdWords, but it's better off ignoring that slight and continuing to cash Amazon's checks. Meanwhile, Amazon has a huge user base, but paid search ads with Google are a powerful way to acquire new customers.

These two companies might both want to take the other's customers, but the advantages of continuing to work together -- even if they're both working toward hurting the other -- outweigh the gains from not doing so. 

Daniel Kline owns shares of Apple. The Motley Fool recommends, Apple, eBay, Facebook, Google (A shares), Google (C shares), and Yahoo. The Motley Fool owns shares of, Apple, Barnes & Noble, eBay, Facebook, Google (A shares), Google (C shares), and Yahoo. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.