What's the significance of this? Twitter Inc is governed by US law, it is obliged to comply with NSA-driven court requests for data. Data stored in Ireland is not subject to the same obligation. Twitter is not alone in using Dublin as a base for non-US operations; Facebook is another company that has adopted the same tactic. The move could also have implications for how advertising is handled in the future.
Ireland is widely recognized as having the most relaxed privacy laws in Europe, and this is something which is important for any company looking to monetize user data through advertising. While data that is processed in Europe may be beyond the immediate reach of the NSA, the policy change could also be seen as a way of trying to sidestep future legislation which may make it more difficult for US-based companies to share data about European users with advertisers.
The changes kick in on 18 May 2015 and Twitter briefly explains them in a policy update post:
If you live outside the United States, our services are now provided to you by Twitter International Company, our company based in Dublin, Ireland. Twitter International Company will be responsible for handling your account information under Irish privacy and data protection law, which is based on the European Union’s Data Protection Directive.If you live in the United States, the services will continue to be provided to you by Twitter, Inc., based in San Francisco, California, under United States law.
Of course avoiding the NSA or making advertising easier are not quite how Twitter explains the reason for the change:
As more people around the world use our services, we’ve expanded our operations to improve how we support our users globally.