Imagine I'm in the EU, and Facebook wants to store my data in the EU.
But I'm friend with US people. So I'm in their own friend list too, which is stored in the USA. So my data is needed in the USA too.
When I publish something in Europe, my friends needs to see it too in the USA. And you can't build a Facebook wall with intercontinental latencies. You need replication.
It's a social graph, and you can't split it between US and EU: data has to be replicated across borders (or face massive latency and bandwidth).
I think this relates more strongly to things like the fb tracking through like-buttons, building a shadow profile of your online activities and such - and moving that data from an EU data centre to an US one. It might also relate to storing archives of private messages you've "sent" to other users - "transferring" a message from you, in the EU to a user in the US isn't part of this -- transferring your entire chat history from the EU to the US might be.
I don't think published messages to people you have chosen to share them with are the kind of information at issue here. Otherwise this would also affect email being sent across the Atlantic.
You're completely missing my point. Your facebook user name isn't personal private data, it's explicitly public. If people in the US have your name in their friends list that list belongs to them, not you. Not even the bit of it with your username.
> And you can't build a Facebook wall with intercontinental latencies.
I have yet to see a Facebook wall in under 0.133 seconds, I'm not sure intercontinental latencies are the biggest problem in web performance these days...
The latency would be incurred several times when loading a single wall. As an experiment, take a moderately complex web app and deploy it in a different continent from the database it connects to.
If you're at the point of storing data on different continents and being aware where it is stored, I'm not sure what is stopping you from batching your trans-continent queries so that you only hit the trans-continent latency once.
When I publish something in Europe, my friends needs to see it too in the USA. And you can't build a Facebook wall with intercontinental latencies. You need replication.
It's a social graph, and you can't split it between US and EU: data has to be replicated across borders (or face massive latency and bandwidth).