It will give an error at some point. Sounds like your friend is just cheap. Just yesterday I was involved in a similar discussion. My father in law does not copy his photos to the computer. That is not even a thought to him. Camera's have nothing to do with computers, why would be think of doing that? He just takes the memory card in and selects the photos he wants printed and is done. When he needs more space he deletes some in camera. To him it is all about the hard copy.
Just a few weeks ago he wanted to get a couple of pictures enlarged. His first thought was to take in a print and get them to scan it to enlarge it. It never occurred to him, until we mentioned it, to take in the original digital copy and have them use that. He did that, but never gave it to me to tweak first (one of them is crooked and the other has red eye).
We told him that if he does not keep a copy it is the same as not having the negative. He said he could never find those either
To top it all off, it would not be hard to copy. His computer has a build in card reader!