It's a bit strange to call it shifting when the profits were made overseas. And it's no surprise they'd keep it off shores once they've made it, since they'd have to give up 35% of it to bring the money inside the U.S.
I'd say that it's hardly tax avoidance, since they pay their taxes in the countries where the revenue is generated. No one in their right mind would give up 35% of their wealth simply to move it to a different country, and nor should they.
Sure, but is it really operating out of Luxembourg? I suspect most of their employees are here in the States.