Google expanded on Wednesday the reach of its new sharing button, dubbed “+1?, introducing a version that companies can add to their websites, alongside Facebook and Twitter’s now ubiquitous Like and Tweet This buttons.

The button has little benefit currently, but it’s clearly part of the infrastructure for a bigger project — Google’s long-rumored social networking competitor to Facebook. It’s like putting a way to fill your cart before the cart and horse.

The button allows signed-in Google users to recommend the page to their friends and contacts, who can see the vote and a thumbnail photo of the voter if the page shows up in search. Early partners include media outlets such as Bloomberg, Reuters, The Washington Post and Mashable, and the widely used sharing plug-in ShareThis, which makes a sharing toolbar bloggers and publications can just drop into their site. Extending that reach, the button will also be on YouTube videos, next to apps in the Android Market, on Blogger blogs, and on its shopping search site.

Google introduced the “+1? button on its U.S. search pages in March, but the problem with the button was immediately evident. In order to like a search result, you’d have to either know before clicking on it that you liked it, or you’d have to visit the page, and then return to the search page to vote it up. (If you still can’t see the button and you are in the United States, you can sign up to see it here.)

It didn’t seem to do anything — somewhat like a light switch that doesn’t control a light — because you have no idea when or if any of your friends actually sees your recommendation.

Google is positioning the +1 button as a way to add “social” features to search, adding a layer of recommendations on top of its powerful search algorithms, which are constantly handling sites using nefarious tactics to game their way to the top.

So now, Google says, if you like a news story or website, and the site has the +1, it should help sites get more searchers to visit (it’s not clear yet if the votes will be used to reorder search results, or if they will simply be added as a display element to the normal results.)

Given the centrality of Google to web traffic for publishers and websites (about 40 percent of all traffic in Wired.com’s case), it’s not going to be difficult to convince millions of sites to integrate the +1 button by simply adding a bit of JavaScript code.

One might be tempted to see this simply as a way to keep up with Bing, which is integrating more and more Facebook data into its search results. That’s data Facebook is unlikely to share with Google — given how keenly the two companies see each other as rivals.

But it’d be foolish to think this is simply about search. Facebook’s Like button has been a phenomenal success, letting people instantly share a story or pair of shoes they like with their friends. But that button didn’t come along until just last year, long after Facebook had established itself as the king of social networking and online identity.

Google has watched closely. And it’s going to fill the web with its sharing button, thanks to the power of its search engine. And then when (not if), Google announces its social network, your likes will already be there and the buttons will be there to add even more.

For now, the button doesn’t have much purpose — and there’s not much feedback, because for now you don’t know if anyone even sees your vote. But it adds one key block of wood to Google’s collection of social networking lumber, which includes Maps, YouTube, Google Profiles, HotPot, Buzz, Gmail and Android.

Now it’s just a question of whether the tinkerers at Google nail those pieces together to build a house for your online identity that you’ll prefer to Facebook’s — or at least one, you won’t mind having as a second online home.