Another shot has been fired in the war to own the social career networks — TechCrunch reported today that LinkedIn has cut off access to its data to both BranchOut and Monster’s BeKnown.

As we’ve reported, both services are designed to leverage Facebook’s social graph and more than 750 million users to help them find career opportunities through their friends. Until LinkedIn’s move, they had been able to use the API to give those Facebook users a shortcut in creating a resume on their own services, making them easier to set up.

As this conflict unfolds, we are going to hear a lot from each party about how they are acting in consumer’s best interests, while the other side is trampling their rights. Don’t be fooled by the rhetoric though — all three companies are simply following the money and acting for their own best interests.

LinkedIn has not yet commented publicly about this situation, and its blog doesn’t even hint that anything out of the ordinary is going on. But when it does, LinkedIn will likely claim that it is protecting its users’ privacy. Who could argue with that?

But the real motivation here is something else. LinkedIn’s rapidly growing business depends entirely on its proprietary data; there’s just no way that it is going to let other companies use its own data to compete with them. In fact, the LinkedIn API’s Terms of Use, section 1.5.n., explicitly states that companies using the API agree not to “use the APIs in an Application that competes with products or services offered” by LinkedIn, something that Monster and BranchOut were surely aware of when they built their applications.

Monster’s Vice President of Product Management Matthew Mund posted Monster’s official response to the API shutdown. In it, he says:

We are disappointed by this decision. Why? It’s not good for LinkedIn users: blocking the API effectively limits LinkedIn members’ ability to import their own profile data or invite their own connections to another environment, whether BeKnown or others.

See? Monster is doing this for the poor suffering users who just want to post their data anywhere they want.

Except that Monster’s entire business is charging for access to a closed database. In the Monster Terms of Use, the company specifically prohibits anyone who would “aggregate, copy, or duplicate in any manner any of the Monster Content or information available from any Monster Site, without express written consent from Monster.” What’s good for the LinkedIn goose is clearly not good for the Monster gander.

As for BranchOut, its public position is similar to Monster’s. As the new kids on the block, it also seems happy to be getting this kind of attention, and used its response to the TechCrunch article to promote the superiority of the Facebook audience over LinkedIn’s.

This move by LinkedIn will not greatly hurt either BranchOut or Monster’s services in any big way — importing a resume was just a convenience for their users, who can still create profiles the old-fashioned way. But its a clear sign that LinkedIn recognizes that these services are taking aim squarely at its market, and that it won’t just roll over and let them do it.

Or to quote Monster VP Eric Winegardner, “game on.”