If you ask Facebook, the IRS hasn't even settled the matter of how much that property transfer was worth. It's still "in dispute," the company says. Not that the agency is likely to show much sympathy, as it has repeatedly fought with Facebook over the auditing process. The IRS maintains that Facebook didn't produce all the data it needed for an audit and didn't show up to meet auditors, while Facebook insists that it bent over backwards to supply info and make staff available.

Companies won't get to use the loopholes in question after 2019 thanks to changes in Irish law, so Facebook may not run into a tax dispute like this again. However, it's doubtful that Zuckerberg and crew will take much solace in that fact. The whole point of the Irish presence was to minimize taxes -- it's reasonable to say that Facebook will fight tooth and nail to preserve the benefits of its creative accounting.