Has anyone suggested private photo mode, like private browsing mode where the photos aren't automatically synced or backed up to the cloud?
You have to go to iCloud -> Storage and Backup -> Manage Storage -> Camera Roll to turn it off.
Unless you mean that iCloud backup itself is not turned on by default, which is accurate. But the way you worded it it reads like if you have iCloud backup, it won't backup photos until you expressly tell it to which is inaccurate.