Speaking second-hand here; my brother is an Apple devotee and a music buff. For many years, he collected recordings of live music shows. They were rare if not entirely transient (in that it would be impossible to reacquire them if lost), and he had a good library of them. Stored on his iMac. Then (as he tells the story) one day iTunes decided to replace all of his rare recordings with the equivalent studio songs. They were gone, and the support personnel he contacted told him they could never be recovered.
He still uses Apple computers, but I don't think that wound will ever fully heal.