While Google+ Local is a free platform, 'Local' is just one of the content pieces of a huge monetization puzzle, that helps to create billions in revenue for the company.

Below is a great infographic from WordStream that illustrates the big picture of how Google+ Local fits into Google's mobile monetization strategy.

Google's Mobile Products: How Google Makes Money from Mobile | WordStream

The mobile search market is experiencing out-of-control growth. Mobile searches have increased 200% year over year in 2012, and it’s predicted that within the next year, mobile will become the primary way people access Google’s services...

...Google has managed to transform itself into a “mobile first” company. Currently, the majority of Google’s $8B run-rate mobile revenue derives from advertising (excluding Motorola). That’s why the company is totally restructuring the way its pay-per-click advertising platform, AdWords, works – Google wants more businesses advertising on mobile, so it’s making mobile PPC radically simpler with the introduction of enhanced campaigns, as well as new mobile conversion types, offer extensions and a mobile app ad type, all specifically created to address mobile-centric use cases...

New research conducted by WordStream into Google’s mobile product portfolio reveals that Google’s mobile strategy centers around investments in four key mobile product areas: Mobile Devices, Mobile Apps, Mobile Content and Mobile Advertising.

In the below graphic, we outline Google’s top 20 mobile products, including a report card that grades each product based on quality, adoption, originality, value to advertisers and other criteria. Scroll through to learn what each of these products does – and how they add to Google’s bottom line! (Click on the image to enlarge to full size.)