Does that mean that if a door isn't locked, it is an invitation to enter my house? Take a look at the case of Andrew Auernheimer (mentioned in the OP) who could be sentenced up to 10 years in prison for accessing data on a web server that was unsecured (http://www.technewsdaily.com/15581-hacker-found-guilty-despi...)
The fact the webserver willingly gave the information I requested to me (did not 403 or 531), so I must be authorized.