per object. So although the chance of losing any particular object is tiny, the chance of you losing something is proportional† to the number of objects. Still extremely small.
†roughly proportional if you have << 1e11 objects
†roughly proportional if you have << 1e11 objects
Similar deal for hard drive bit error rates, where the quoted average BER may not necessarily accurately represent what can happen in the real world. For example, an unrecoverable read error loses 4096 bits (512 byte sectors) or 32768 bits (4k sectors) all at once, rather than individual bits randomly flipped over a long period.