For plain files, pick your risk tolerance. For DB backups, until you've actually loaded it back into the DB, recovered the tables, and tested a couple rows are

For plain files, pick your risk tolerance. For DB backups, until you've actually loaded it back into the DB, recovered the tables, and tested a couple rows are bit identical to the source, it's a hope of a backup not a backup. Things like weird character set encodings can cause issues here.