People who don't think it's a big deal that corporations have been elevated to the status of a person fail to appreciate history. All the founding fathers, and the country as a whole, were very suspicious of corporations and strictly controlled them.
They fail to appreciate the economic power of corporations (many have the wealth of mid-sized nations), and they fail to appreciate the simple fact that corporations are legally bound to further the interests only of their shareholders - society at large be damned.
The Supreme Court's elevation of corporations to personhood means that governments are very limited in the regulations that can be imposed on these entities, which is a potential - and very real - danger to us all.
For all those who think a corporation really is a person - including Mitt Romney - I suggest they take a corporation to dinner and see how that works out.