[chiph]

Who gives their phone number to store clerks? "Sorry, it's unlisted."

[breitling]

As hard as it is to believe, I'm sure plenty of people give out their phone numbers when asked. I have personally witnessed many many people (including my wife) give out their number at checkout without hesitation. I guess the fact that this is continued practice means that it actually works.

This may vary by geography...my observations are from Canada.

[prostoalex]

Large department stores would frequently pitch a loyalty card that's then tied up to your profile, for a which a phone number is frequently a must.

[sp332]

It's s numbers game. If store clerks ask everyone, all the time, then enough people will answer for the practice to be useful.

[oliyoung]

I'd argue that any HN member (or even any 1/2 tech savvy consumer) isn't exactly their target market