Google has begun experimenting with a feature to customize search results to reflect your online social network. The idea is to give extra weight to information and opinions from people who you have already formed an online relationship with such as friends and colleagues.

The new Social Search feature will take particular account of posts from your friends and contacts on various social network sites such as Twitter and FriendFeed, along with people who you’ve contacted via Gmail. As well as searching posts, the feature also looks at pages which are linked to in those posts.

The theory is that this helps improve the relevance of search results by building on the trust you have in the opinion of friends and contacts. For example, if you are looking for a hotel to stay in during a citybreak, the Social Search results can bring up comments your friends have made about hotels in the area. In some cases this can extend to friends of friends and so on.

Users can switch between having the Social Search results built right in to Google’s SERPs or viewing them in isolation.

Google stresses that the service isn’t a threat to privacy as it only covers content which is already publicly available. However, using the site does mean telling Google which social networks you are a user of (though, of course, not handing over passwords.)

One limitation of the service is that it’s only available to people who’ve created a Google public profile and then linked their various social networking accounts from it. It’s currently only available as an experimental feature through Google Labs, where users are limited to one such feature at a time.