Yes, I understand you don't want to give that information out

[Ree]

At our old store, we used to put in the customer's phone number if they were ordering something, or if they bought an item that came with a 1 year replacement warranty (which is just about any small electronic appliance or power tool we sell).

Customer info was stored only in our store database, and it was so easy to just look up a customer by phone number to find a sale if they forgot their receipt when doing a return, or if an error was made on their sale and it needed to be fixed.
We had several people who were so incredibly paranoid about what we were doing with their phone number. In some cases, they refused, and in other cases, they gave a fake one.

I can recall at least 3 separate occasions when there was a newbie cashier, or a really bad cashier, and mistakes were made in our favour.
After I fixed them, we actually owed the customer money, but because they had given me a bogus phone number, or refused to give me their number, I had no way to give their money back to them. They never noticed the error, either. It all just sat in envelopes in the petty cash drawer.

I have no idea what finally happened to it.

We also had a customer who was given the wrong item.
He got the cheaper item, but was charged for the higher priced item. When the customer who actually ordered the cheaper item came in, we couldn't find it.

Again, because we had been given a bogus number, the guy ended up getting ripped off. He never came back in to return the item.

We do the postal code research every now and then, and it's all strictly voluntary.
We do it so we can see if there is an area to which we aren't currently advertising, but are getting a good customer base from.

On our new system, orders are entered by name, and if there is the least little error or alteration in spelling, it's impossible to find the sale.
Phone number lookup was just easier.

[TryNotToBeThatOne]

Then there was the delivery driver who scolded me for not giving my phone number when I placed the order. Yeah, except that I could see it on the paper slip that he was holding.

To be fair, I was waaaaay out of town at a convention & had given my cell number so it had a peculiar, to him, prefix. Nonetheless, what other 10-digit number would I have provided?

RE the OP,
Appropriate responses when the cashier asks for your zip:
1) your zip
2) 'I'd rather not'

or even

3) shop somewhere else (good luck with that one)
4) complain later to Corporate about the policy (good luck with that one, too)

Inappropriate responses:
1) 'Why, you wanna hook up?'
2) 'I want to speak to your manager'
3) 'I don't hafta give you that'
4) your phone number

[Mike Taylor]

Same with me. Thankfully, Best Buy seems to have stopped asking, but I think Toys R Us still does it.

The one time, I was in kind of a mood, when the cashier asked for my number, I asked why it was needed. Her answer (or non-answer in this case) was "It's store policy."

I decided not to hold up the line needlessly, and gave her the number of second line I had for dialup at the time. I didn't care if they called that one, as there was no phone connected to it, only a computer.

Best Buy got a ton of complaints and quit doing it some years ago. TRU, on the other hand, still does.

In relation to the Reward Zone (points card) that Best Buy has, the floor associates are supposed to offer that to the customer well before they get to the checkout. That way, the customer that is interested in it can ask for it. They usually do if the sales associate has presented it in the right way. Same for the Reward Zone Mastercard. The cashiers also ask, but they understand that not every one will accept.