Google announced this week a new social search feature called +1. The new offering competes in some ways with Facebook's "Like" button.

By clicking on an optional new +1 button on your Google search results, you can tell family and friends that you recommend certain links.

Big deal, right? Well, actually, it could soon be a very big deal.

What Google's +1 adds up to

Google's +1 isn't what Google would call a "shipping" product. It's a "Labs" experiment, a cross between a beta program and a trial balloon. But it's available to everyone and easy to use. You just go to the Google Labs page and click "Join this experiment" in the section about +1. Once you've done that, when you're searching on Google, you'll see a +1 button on every search.

All your +1 recommendations are retained on a new tab viewable on your Google Profile. You can choose to make them public or keep them private. (I've made mine public -- you can check my +1's here.) Also: When your Google contacts conduct searches of their own that bring back links you've flagged with +1, they'll see your recommendation on the results page.

For now, the feature is limited to Google Search. Google plans to roll out the feature for websites of all kinds, including blogs.

Google also says it plans to "record information about your +1 activity in order to provide you and other users with a better experience on Google services." That could mean just about anything, although Google says +1 activity does not affect search rankings.

How +1 is like, and unlike, 'Like'

Once Google offers the ability for website owners to add +1 buttons on their sites, the service will be a lot like Facebook's "Like" feature. With Facebook, everything you "Like" anywhere on the Web is viewable by friends on Facebook. And that's one of the differences.

With +1, your recommendations are currently unlikely to be encountered "in the wild" by contacts. It requires both opt-in by contacts, plus the unlikely event that the other person searches for something you've already flagged.

Google +1 is currently useful only for seeing someone's preferences after you've run across them on your own, while Facebook "Like" is better for discovery. Both could be a lot better for discovery. What's missing from both Google's and Facebook's recommendation engines is the ability to pool all that data in a single space. The ultimate application would be open APIs by both parties, with some scrappy startup building the ultimate Digg replacement site where both systems are combined into a single popularity contest for content.

One advantage of +1 over Like is that it lets you recommend things without appearing to approve of them. When I encounter a blog post headlined "Tickets for Apple's Developer Event Selling for $3,500 on eBay" and click the Facebook "Like" button, it appears on my Wall above the phrase "Mike Elgan Likes this." It makes me look like a sociopath. Google's +1 is more neutral.

Google currently has two incompatible systems. You can click +1 on search. But on Buzz, where the +1 could really find some use, Google uses the word "Like" in a system that's disconnected from the +1 recommendations. This is especially awkward because Google went to great pains to connect Profiles and Buzz. But +1 recommendations show up in Profiles, and "Likes" remain in Buzz. It's a fractured mess. Meanwhile, Facebook's "Like" system is unified.

Why +1 and Like matter

Social recommendation tools like +1 and Like can potentially help users do things such as the following:

• Get and give recommendations to friends (replacing link sharing).

• Bring attention to cool stuff (replacing or enhancing Digg and Reddit).

• Bookmark and remember things (replacing browser bookmarks, Instapaper and StumbleUpon).

• Set up popularity polls (replacing poll plug-ins on blogs).

• Engage in social science research (replacing text-based voting on American Idol).

The exciting thing about the Like-button concept is that it can, and probably will, spill over into the real world. Within a few years, you'll probably be able to "Like" TV shows, locations (via existing location-based services like Foursquare, Google Latitude or Facebook Places.

Smartphone app-based services are getting better and better at recognizing songs and TV shows (by the sound), and soon they'll be able to recognize objects that you photograph with the camera in your phone. So you'll be able to "Like" all kinds of content and objects in the real world.

Google's +1 system is new and experimental and therefore isn't changing the world yet. Facebook's "Like" system is becoming influential, but it's still overshadowed by Twitter, link sharing and other ways of sharing and recommending content.

The reason this is a big deal is this: History tells us that obscure, trivial services like Twitter and Facebook and even Google itself can rise to dominate user attention, and make billions for the entrepreneurs who get it right. Whoever dominates "Like"-type services could end up making enormous amounts of money.

The whole "Like" idea is potentially superior to link sharing, bookmarking, social bookmarking, polling and other technologies that millions of people use every day. If the concept really takes hold, it could become the primary way for people to share content, links, opinions and much more.

And don't even get me started on the marketing potential. Once companies get us to start "Liking" and recommending the products and services we buy, they'll have found a lucrative enhancement to advertising and marketing campaigns.

Google +1, Facebook "Like" or some other service we don't know about yet could one day rise to dominate the lucrative new world of social influence.