Why would European regulators even care about Facebook? It's a completely voluntary service and anyone's free to create an alternative. It's non-essential.
If a huge U.S. retailer muscled into the EU markets and started driving mom-and-pop retailers and smaller chains out of business, I can see where the regulators would go nuts and try to stop them. It's a clash of U.S. capitalism versus European style capitalism and if they don't like the raw knock-down-drag-out American approach, it's understandable.
If huge Asian car manufacturers started undercutting European makers with high quality, low cost vehicles, causing thousands of factories and parts suppliers and dealerships across the continent to go out of business, I can see how regulators would want to limit or stop the disruption.
But Facebook? Just don't use it. Don't browse to facebook.com, problem solved. Nothing is affected. What am I missing here? It looks like just another shakedown of a highly successful foreign company that the regulatory bureaucracy regards as a threat of some kind. Too profitable, too entrepreneurial, too brash -- some combination of too many ick factors, I suppose.
As jakozaur says, why not promote and encourage domestic competition? There are brilliant computer folks in Europe and I'm sure they can come up with a few classy, high quality alternatives to Facebook. As an American, I'd love to see some competition to FB.