I have a Tesco clubcard, but it doesn't seem to work the way Grab's does. He says they send him money off vouchers for his favourite crisps. I find they use the profiling to try to sell me things I wouldn't otherwise buy from them.
e.g. If I buy a cheap instant coffee they will send me money off vouchers for expensive coffee to bring it down to a comparable price. Clearly their hope is that I will continue with the more expensive version even after the vouchers stop.

My favourite vouchers are sent out by The Daily Telegraph. They seem to compile a list from those who enter their competitions or crosswords. The vouchers represent a saving on the purchase of The Sunday Telegraph (which I would buy anyway) and the vouchers are idividually dated for a period of up to 3 months. As I have relatives who also get these vouchers (at different times) but don't read the Sunday Telegraph, I seem to have vouchers for use most of the year.

Nigel