Can Google sustain its awesome side projects with decreasing ad revenue?

With buzz building about Google's newest project, the build-it-yourself smartphone known as "Project Ara," it's worth noting that some company observers are concerned about what Google's side projects are doing to its profit margins.

The tech giant is set to report earnings for the first quarter of 2014, and while analysts expect that it will post solid revenue, a growing number of voices are asking whether the company is spending its money wisely.

Google is, primarily, a search and advertising company. But it's clearly happy to invest in a variety of other projects that aim to tackle big problems and new challenges. These, in turn, offer Google new ways to make money -- something that's particularly important as the average cost of an online ad drops, and Web users shift more heavily to mobile devices, where the ads aren't as lucrative.