From the Tesco.com website...
Marketing and research
If you agree, we may contact you:
* with offers and information about Tesco products or services
* with offers and information about partners' products or services
* for customer research eg to help improve our services
Of course, the choice is entirely yours, but if you say you do not want to receive marketing information from us this will prevent you from receiving great offers or promotions that may be of interest to you.
When you register online you can access a "Contact Preferences" page that allows you to tailor our commercial communications to your preferences.
To change your contact preferences simply click "Your Account" in the top frame and click "Your Contact Preferences". If you do not want to receive commercial communications from us, select your choices by using the boxes available on that page.
We like to hear your views to help us improve our service. From time to time, we may contact you to ask your opinions. Again, if you do not want to be contacted for this purpose, make your choice on the "Contact Preferences" page.