mw1234's comments

I think that is a decision best left to the developer or user. Take an app that syncs your photos from a site you may already use, like Picasa, Flickr or SmugMug. You want to have these available on your iPad or iPhone instantly, even when you are without internet service. But you don't need them backed up to your computer every time you sync, causing the backup times to skyrocket, and if you lose them on a restore, it's a minor inconvenience, but not a huge deal. Losing them unexpectedly when you don't have the time or ability to re-downlaod them is a much more major problem for some people.

You are missing "No backup, never cleared" which is what the old "2. Cache" scenario used to be.

This is also particularly problematic for my own apps, which are offline photo browsers that sync your collection of photos. Keeping GBs of data in the Caches folder was the only way to have iPhone backups occur reasonably fast. Sure, they can be re-synced, but that will be a very time-consuming process for thousands of photos.

Should the calculus for banning vehicles or alcohol be any more complicated than whether they enable more drunk driving?