[daveoc64]

The system originally worked on an overnight batch processing basis.

Each store would have a local copy of the card balances - but only for cards that had been used in that store in the past 12 months.

The first day you scanned your card in a store, you could only collect points (not redeem them).

By the next morning, your card would be included in the local database and you could redeem points - with the vulnerability that each store had its own database, and therefore you could redeem the points in multiple stores.

I thought this had been improved in recent years, but maybe not.

[Suppafly]

Everything that normal people don't like about the user experience of large computer systems can be attributed to the batch nature of how these systems were designed and often still operate. A lot of systems that feel real-time are really just batched more often.

[sp332]

Is there any actual identity connected to these? A way to find the person and get the money back?

[daveoc64]

You can register a Nectar card (giving name/postal address/email address/phone number/date of birth), but I'm not sure how much verification of these things they do.

I am not sure, but I think you might need to register to redeem points.

[rwmj]

There would be CCTV and maybe more if they used a payment card for the purchase. Whether Sainsburys would lift a finger to investigate a small loss is another matter.