I think the point being made here is only valid when you just move the data around and don't alter it. filepicker is a perfect example where you pass the data around without actually touching it and such a usage is a perfect case for passing the "pointers" around. In most other cases, you'd want to pull it down the moment you are going to transform it.
Even if you're going to pull it down, passing an URL around is still better. It means the client software can schedule the download for a few minutes or even hours to reduce peak bandwidth demands, they can PUT an updated version back, they can poll for changes, etc.
