That won't work as I already have loads of pictures in my iCloud account which Sync won't pull out and backup as it thinks the files are the same. At least that's how it looks like what Sync is doing after testing a couple of days which even included a factory reset. To me this is a bug/error/glitch or something that makes Sync not working as intended. It does backup the Camera Roll but only the files that are named in a certain way. I would suggest it's stated very clearly that Sync will not work in cases like this, ie. it can't handle users who have switched phones and starts naming photos with the same names as already are in eg. their iCloud account. Those pictures won't be backed up. This in practice means that you have one phone for a year, you shoot 2000 pictures and those are backed up my Sync. All is fine but then you switch phone and start using Sync again. The first 2000 pictures you shoot with your new phone won't be backed up but you will still have 4000 pictures in iCloud. I do agree backups should be kept 1:1 - but for everything besides photos. Those are better identified with eg EXIF and is what Dropbox and Google Photos are doing. Just because anything else will fail in the end.