I don't have a Google Plus profile for my Google account so I can't get to the checkbox to opt out without first creating a creating a Google Plus profile. Talk about a catch 22. Though maybe they're only planning to use Google+ content for ads?
If you don't use G+ there is nothing this opt out would do. This is an opt-out for having your G+ profile picture and name show up next to search results for people who have you in their circles. If you +1 a page, then that page can be promoted in your friends search results with your name linked to the page. It's actually a fairly useful feature and I often see Android links promoted by people I have added to circles, which is useful.
It's really a fairly benign feature to begin with as you have to actually +1 a page before it shows up. At any rate, this checkbox appears to remove that so that others can't see your +1s in search results. I don't really understand why you would +1 something and not want people to see though, although I'm guessing it has something to do with an employee of companyA +1ing companyBs page by mistake and making it look like an endorsement.
