Facebook has explicitly stated that it does not fear Google+. That Google's latest social network effort simply validates Facebook, but does not threaten to replace it. This may be true, or it may be a public act.
Either way, Facebook isn't taking any chances.
Mark Zuckerberg's company moved quickly to block Open-Xchange's export tool, which used Facebook's API seemingly legally to transfer a contact list from Zuck's town to Googleville in one fell swoop. Of course, anyone can manually transfer their contacts, but considering how labor-intensive this method is, few are apt to do it without some form of efficient automation. But Facebook has been firm in denying such an opportunity. Is this a sign of fear, or simply defending its API usage policies?
Google+ has roughly 4 million users now. Facebook has more than 750 million. Relatively speaking, Google+ is not even a blip on the radar. But in absolute terms, given how new the service is, 4 million is a formidable number.
It's easy to say that Facebook has too much of a stranglehold on social networking for Google+ to compete. But did people not say the same thing about MySpace, which recently sold for just one percent of its peak valuation after a lengthy and uncontrollable downward spiral? Then again, MySpace made a lot of foolish mistakes that Facebook has yet to replicate. And MySpace also never came close to 750 million users, either—let's note that this is more than 10 percent of Earth's population, and a much, much higher penetration than that when you consider all the babies, very old people, and people dwelling in third-world countries who are obviously not in a position to become Facebook users. Of all the people are are eligible Facebook users… a lot are.
Facebook is being, at the very least, cautious by blocking automated export tools. They know that people are lazy, and having a simple way to transfer their contacts makes or breaks whether many will use a particular service. Nobody wants to re-build their address book for a new service unless it is absolutely magnificent. Facebook was good enough to qualify for this. Whether Google+ qualifies remains to be seen.