[sjwright]

A summary of the tax arrangements used by some large American multinationals, including Microsoft, Google, Facebook, Apple, Oracle and Adobe:

http://en.wikipedia.org/wiki/Double_Irish_arrangement

As I understand it, these international profits remain in the tax-haven-resident Irish company, and cannot be repatriated to the US parent without incurring an undesirable taxation event.

It's highly likely that Finland-based Nokia is a fiscally efficient purchase for Microsoft. Both Finland and Ireland are EU countries, are in the Eurozone, and have a customs union.

(It would be interesting to compare this to Google's purchase of Motorola Mobility, which was an American company.)