You may have missed this one from yesterday, buried under all the headlines about Facebook overtaking Google in the U.S. The two web traffic giants are pushing ahead with their own respective “social search” offerings. What does this mean for big brands?

Social search promises to be a more timely, more credible and more local way to search for tips on new products, plus film and restaurant reviews or, simply, to stay in touch with what your network is discussing at this very moment. As SearchEngineWatch explains, “The idea behind social search is basically to get the input of your friends, rather than anonymous Web sites.”

With Google’s Social Search, results are culled from your connections and presented on a search results page.

And Facebook? Wayne Kao, a Facebook engineer, explains on the company blog that starting this week social search results will appear as you type keywords into the search bar. He explains:

Now as you’re typing in a query in the search bar, you will instantaneously see results not only of the people, events, groups and Pages you’re connected with but also the connections of your friends and globally relevant results. You’ll see a wider variety of relevant results and be able to discover new connections you might want to make on Facebook right as you’re entering your search.

We tried it out with Guinness, today, of course, being Saint Patrick’s Day. The results? It’s not even noon yet in Dublin and already the Guinness-referenced updates are streaming in at a clip of every few seconds across the entire Facebook network.