Yes, photos will be backed up through the normal, iCloud backup. Photostream is really more about having your recent pictures available for viewing on all your devices than for backups.
Yes they will be backed up, but you can't view them in iCloud.
iCloud back up will store the photo's in the camera roll, and should you ever replace your phone and set it up using the same iCloud account, they will appear in the same place.
I disagree, but we can talk about it.
I'm taking the OP literally to mean he want's to save a picture forever. As already mentioned, Photo Stream does not back up photos. However, Photo Stream can deposit photos on a computer where they are stored until you manually delete them (your computer is the backup). For me Photo Stream sometimes fails to transfer the pics.
I would not rely on iCloud as the backup for your photos until it is more mature and there is a better understanding of it. This means using Photo Stream or a normal iTunes sync to put pics on your computer. Two main reasons: 1) An iCloud restore is an image restore, meaning all or nothing. It will overwrite any photos on the phone that haven't been backed up yet. Depending on why you're restoring and if you could do one last incremental backup it could mean a loss of photos. 2). At some point you will have more photos in your iCloud backup than can fit on your phone. I haven't seen a discusson on what happens when you have 80GB of photos and restore to a 64GB phone.
So it's mainly fear of the unknown. I use the iPhone as my primary camera and take pictures of 'da kids. It would kill me to lose even one of those pics. I use Photo Stream and when it fails
I copy the pictures over to the computer by hand. Those pics are then backed up offsite via Carbonite.
