By that argument, an exchange is a legally defined concept and MTGox isn't one of those either. MTGox is not a legally regulated bank. They are not a legally r

By that argument, an exchange is a legally defined concept and MTGox isn't one of those either. MTGox is not a legally regulated bank. They are not a legally regulated exchange. They DO hold accounts on behalf of their customers, performing the function known as "banking". They DO execute trades between their customers, performing the function known as "an exchange".