It didn't do much for the 'ordinary citizen' despite what the author of this article says. The best put down of this document is to be found in "1066 and All That" by Sellar and Yeatman. Several articles of the MC are followed by the statement "except the Common People." In reality, it was a charter for the Ruling Class against the king, nothing more.
1066 and All That: A Memorable History of England, comprising all the parts you can remember, including 103 Good Things, 5 Bad Kings and 2 Genuine Dates. Extremely funny, but you have to know the real history to realize how cleverly screwed up the history is in this book.
That's true, but it was part of a process that eventually lead to the Declaration of Independence.