You could edit the document if you had a Google Account. Unfortunately, only the first 200 people who sign in to the document can edit it (this is a limitation in Google Docs).
The document is public and will be updated after every change.
Update: 18 hours, 3010 revisions and 500 collaborators later, the 1871 words document has an interesting shape. For some reason, more than 200 people could sign in and some of them actually deleted the whole thing or duplicated the text. But I think this shows that Google Docs could become at some point a way to build cool wikis and that the selling point of Google's office suite should be collaboration.
Note: The document is no longer editable. Thanks to everyone who took the time to write something.