Never mind the fact that most of the people you know aren't using Google+, the US Federal Trade Commission is reportedly expanding its antitrust probe of Google to include scrutiny of the social networking service.

At issue is whether the company is giving preference to its own services in search results, and whether that practice violates antitrust laws, according to reports from both Bloomberg and Reuters.

The issue is timely because Google this week introduced changes to its search engine so that results feature photos, news and comments from Google+ postings. Google calls the new function Search, Plus Your World.

Google+ users now see personal information about their friends included from the social networking service when they conduct a search on Google. Bloggers, privacy groups, and competitors now say the inclusion of Google+ results unfairly promotes the company's products over other information on the web.

The Electronic Privacy Information Center urged the FTC to investigate Google for the search changes, while Twitter complained in a public statement that changes in Google's search engine could make finding Twitter posts on news events more difficult.

Danny Sullivan, the founder of Search Engine Land, wrote in a blog post, "Google's job as a search engine is to direct searchers to the most relevant information on the web, not just to information that Google may have an interest in."

User reaction has been mixed, but some favour the new capability.

In its monopoly investigation, the FTC is focusing on whether Google unfairly ranks search results to favour its own businesses, increases advertising rates for competitors, and uses its control of the Android mobile operating system to discourage smartphone makers from using rivals' applications.

To turn off the social search function for individual searches by clicking on the globe icon on the far right of any search results page. To shut it off permanently, go to your search preferences, scroll down to "Personal results" and select "Do not use personal results". Then click on "Save" at the bottom and watch your friends disappear from your search results.