Searching Google for movie times, liking your cousin's beach selfie, or tweeting a favorite recipe; these things all seem like they are free, but they are not. They all come at a price, such as your data, which could include details on your identity, browsing habits, known contacts, or whatever information may help another company profit from you in the future. Our personal data is a currency, with which we pay the invisible fees and tolls collected in return for traversing the wild expanse of the internet.
Google and Facebook have schemed up their own options which offer you some semblance of control over what information you share with web and app developers. We are talking about each company's individual offering of identity verification for login services. If you haven't used one, you most likely have seen the option. Essentially you are granting one company which you presumably trust, the right to manage your identity, and private data online, in return you get one username and password that unlocks numerous accounts and services across the internet. It is the sort of deal that could only make sense on the internet: to prevent a bunch of companies from having access to varying bits of our personal data, we hand over our master key to one or two corporate behemoths who will dole out only certain bits of information. What are those bits? What information is Google and Facebook passing around when we click that login?
Using Google Login, Google may share your full name, profile picture, Google+ ID, age range, language, the people in your Google+ circles that you've shared with the app, and any publicly available information on your Google+ profile. Much like the permissions in the Play Store, you either accept the bundle of access requests, or you forego the digital goods or service. Facebook offers much more optimization and full control over what a user allows to be shared with a third-party. At the minimum, they will share the user's public Facebook information, but anything beyond that can be accessed and denied from a set of more than 30 configurable permissions.
Again, it comes down to convenience and trust. It really is not in either Google's or Facebook's interest to mishandle users' personal information. Both businesses are massive beyond rivalry in their own ways, but the public is finicky. If either company were to start having major scandals involving their users' data, the user base would revolt. Login services are almost certainly not the final solution to exploring the net with piece of mind. It is also likely that technology will outpace the problem sooner than later. In the meantime, we are left with choosing between having one password that is easy to remember, or 200 passwords that are easier to just reset.