Tom Anderson wrote:
On Sat, 12 May 2007, MIG wrote:

On May 12, 3:05 pm, James Farrar wrote:
On 12 May 2007 06:47:31 -0700, MIG
wrote:

If you really think that collecting data for subsequent mining
is too much trouble, why do you suppose they have supermarket
"loyalty" cards?

For collective data, not for data on individuals.

No, they could get collective data from the till records (eg
buying beer and nappies together). The purpose of loyalty cards
is to get long term data about individuals' patterns of purchases.

Most people pay for their shopping with credit or debit cards. I've
long wondered why they didn't just use the numbers of those to
track people.

Because the credit/debit card number is needed only to effect the
purchase transaction, and any other use not authorised by the card
holder would be in breach of the Data Protection Act. In the case of
loyalty cards, I think you'll find that the terms of use specifically
include permission to track buying habits.
--
Richard J.
(to e-mail me, swap uk and yon in address)