With its recently announced acquisition of CubeTree, you can now add SuccessFactors (SFSF) to the list of contenders, and one likely to move to the front of the pack fast.

The deal, worth some $50 million in stock and a cash payout over three years, is the second acquisition by the newly-public SuccessFactors. It’s interesting because CubeTree, a two-plus-year-old startup, will now have the opportunity to plug its collaboration and sharing services into the 6 million customers already using the human resources and performance software that is the bread-and-butter of SuccessFactors. That includes the 2.1 million employees of Wal-Mart (to be fair, SuccessFactors did not name Wal-Mart, nor has Wal-Mart confirmed it, but please, mammoth retailer with 2.1 million employees? That’s Wal-Mart).

SuccessFactors CEO Lars Dalgaard is quick to distinguish what his company and its new acquisition mean when they say “social.” “What it is,” he says, “Is a set of tools to get stuff done, to share resources and intelligence within your company – almost automatically. It’s the sort of things we do with some difficulty today, via enormous email threads and often by chance.” What it isn’t? “A stream of status updates,” Dalgaard says, “And online chats.”

Carlin Wiegner, CEO of CubeTree, says what he and his team are trying to achieve with their software is to make building a culture of sharing easy within a company. “So that objectives, whether they originate from the top or the bottom, are more transparent,” he says. “And resources and knowledge are easy to tap into.”

Much more in a video here. [youtube=http://www.youtube.com/watch?v=Nr-zpatbPkw&hl=en_US&fs=1&]

That all sounds nifty. Whether it works is, of course, the big question. Collaboration tools have a good track-record in small groups, but scaling some social network for the workplace across hundreds of thousands and in the case of Wal-Mart, millions of employees, has never been tried. The best we’ve done so far is the email blast, or the company-wide wiki (which no one ever used). Wal-Mart (WMT) could be the example that busts this social network at work idea wide-open.

Certainly something, or some company, will flip a switch on the trend very soon, because we are already there in our social lives. There are 400 million people that use Facebook today, and privacy concerns aside, it’s working pretty well. In our non-work lives at least, we are engaging in every social tool we can get our hands and keyboards on. Work will follow. And since it isn’t the same group of people, objectives or behaviors as in our social lives (you’ve learned that now, I hope) it won’t be Facebook that dominates. What company will dominate the “social” network of your worklife? It’s a tight race at the moment, but SuccessFactors just put on a burst of speed.