The accounts inside the VM are separate from the accounts that have permission to operate on the API. The accounts in the VM come from the sshKeys metadata value that the VM sees. This is a union of VM specific metadata and the project metadata. By default gcutil will prompt you to create a key and expand the sshKeys metadata value with that key and $USER. The easiest way to see and edit this is at the Cloud Console. There are more details on ssh'ing into the instance here. - Joe Beda