Customer data - your supermarket is watching you

Supermarkets are getting increasingly sophisticated with how they analyse their loyalty card data.
For example, I am a big fan of Grape Nuts - a rather obscure breakfast cereal. Recently, I was shocked to read that Sainsbury's was thinking of de-listing the brand due to sluggish sales.
Apparently, what saved the day was knowledge from their Nectar card database. Customers who bought Grape Nuts were more loyal than average and had a higher than average spend. So, not wanting to force these customers to go elsewhere for their cereal fix, the store keeps them on their shelves.

You may not have the trillions of records that the US National Security Agency is collecting, but are you collecting and making the most of what you do know about your customers?
If you are thinking of giving up on a lacklustre product or service, just check who is still buying it. If the cost to retain it in your catalogue or available on your website is not large it might have earned its place by the company it keeps rather than simply the profit per transaction.