Last year I lost my package of Aeroplan upgrade certificates when returning from San Francisco. I had been using the envelope containing the upgrade certificates as a bookmark in the book I was reading. I was flying the red eye from SFO to YYZ and, when tiredness overcame me, placed the book in the pocket of the seat in front. And that's where it was when I left the plane.
A book can be easily replaced. But upgrade certificates - they're gold. It's the thought of using them (against all odds) that can make the anticipation of a 14 hour flight to Tokyo bearable. I was not happy when I realized I had lost them.
Coincidentally Aeroplan had just moved to personalized upgrade certs - each had my name printed on it. Aeroplan's motivation was to curtail the thriving black market for the certificates - a market made possible because the certificates were anonymous and so could be easily traded. The new personalized certificates can only be redeemed by the frequent flyer whose name is on the cert - no use selling them because the purchaser won't be able to use them. In order to use the certificates, the required subject confirmation method would have been to separately prove ownership of the subject identity.
If the certificates I had lost were anonymous, I wouldn't have even bothered asking for replacements. Aeroplan would have had no way to ensure that I wasn't double-dipping, e.g. falsely claiming their loss in order to receive replacements for sale. But, because the certificates I lost were personalized, Aeroplan could be at least confident that I wouldn't be able to sell them. And so, I asked for replacements. And, to my surprise, expecting bureaucratic inertia, they gave them to me.
They couldn't be sure I wasn't falsely claiming the loss of the certificates in order to get replacements for my own personal use - I expect they guard against this by watching how many certificates I might try to redeem over the next year.