Giving Out Info

I went to Toys R' Us for a little Christmas shopping the other day.  Just before the cashier rang up my stuff, he asked me for my phone number.

"Why?" I asked.

He shot back a lethargic, "I don't know."

Before I could continue, my wife quickly gave him her cell phone number.

Why does Toys R' Us, or any retailer, need my phone number to buy something?  When did this become a necessity?  What would have happened if I didn't have a phone number?  Would I still be able to give them money?  I paid with a credit card and went about my day.

But it's got me a bit perturbed.  Everyday, we're bombarded with paranoia about protecting our personal information because of: identity theft, phone scams, mail scams, etc. and we are warned NOT to give out ANY personal information.  So, without thinking, I didn't.  I don't like to.

Perhaps it's just the assassin/ninja/C.I.A. Operative nature in me to avoid people knowing any information about me.  I even get uncomfortable giving out my name.