In its TOS, Google has said that it will combine information about the users from various Google services to provide him "better experience." That means, from the data you're updating in various Google services, Google is watching you closely. Know more about Google Plus.
"We may combine the information you submit under your account with information from other Google services or third parties in order to provide you with a better experience and to improve the quality of our services," Google describes in its terms of service.
And they have an additional TOS for Google+, where users upload more information about themselves and about their friends and activities. So, Google not only have have access to your basic details, but also to your friends' through your Circles.
Google Plus TOS reads, "we will record information about your activity such as posts you comment on and the other users with whom you interact in order to provide you and other users with a better experience on Google services."
Google also collects information about you from your friends' activities, posts, photos and even from their Circles and photo tagging. Moreover, Google "may" and 'will' share this infos with the public, our users, and partners, such as publishers, app developers, or connected sites.
"When using Google+ on your mobile device, Google collects your location to provide the service (such as to display nearby posts to you), as described when you sign up for the mobile version of the product."
Just few days after the announcement of Google+, it was praised for the improved privacy and security policies over the much criticized security concerns of Facebook. But, while we dig deep into its TOS, Google+ is set to provide all information about you to its father, the search giant Google.