[neuromancer2600]

I assume most people would first enter their own number to see what this really does. Then they enter all their friends' numbers. Another way to collect address books.

[kmfrk]

Same can be said of many of the websites submitted to HN where people submit their e-mail. There used to be value in keeping your e-mail address to yourself, but it seems people just toss it at whomever willy-nilly these days.

[randallsquared]

Spam control on email is nearly perfect, though. Spam control on my phone is much less so.

[Ilmesnkie_Jones]

Or people have more than one email and some of them are worth less to them than others.

[BenNunney]

Doesn't store data or keep numbers :-)

[kmfrk]

No HTTPS, though. :(

[aroch]

Last I checked your phone number wasn't sensitive information nor does it particularly matter if MITM'd or altered along the way