How would you describe ObamaCare's individual mandate fine?

It's been one week since the Supreme Court's landmark ruling on ObamaCare. In the ruling the high court called the fine attached to the individual mandate a tax. Since then the White House has been holding firm in its insistence that the individual mandate is a penalty. While Republican presidential hopeful Mitt Romney agrees with the court – that it IS a tax. What do you think it is?

This is a non-scientific viewer question.