This +10 (if I could). Putting in something clever (and thus probably rare, and maybe unique to you) can make it far easier for Borg-tronic Analysis, Inc. to connect all the little data dots about you. A bit of data that is common to a large number of people makes a far better poison for their dystopian wishing well.

as someone that had the misfortune of once working for K-Mart, and having management harass us if to few customers gave phone numbers for their rewards account. There were many accounts for jennys number. Also i purchased many pizzas with her rewards account.

Also usually gets you plenty of Safeway Rewards @ Chevron.