If I can ingest contact info from Outlook to LinkedIn, and from Gmail to Facebook... why is it "wrong" for me to carry my social graph data from Facebook to Plaxo, or anywhere else for that matter?
It's not about privacy: every user can control what data does / does not show to others, including their email addresses:
And it's not about protecting Facebook's servers. I'm sure they could accommodate the minimal load involved.
It's about revenue and nothing else. They're afraid that if it's easy for us all to switch to another site, then it can only be bad for them. How sad, and myopic. Facebook provides a lot more value than just the data they want to lock-up.
It seems that ever-prevalent-paranoid-mentality from Redmond has quickly crept into the halls at FB.