Do you have some statistics that prove that users are willing to provide you their phone number as much as their willing to share their email address? I’m curious, because the request for a phone number by services that do not need it for providing their service is a big blocker for me: first I can accept to receive unwanted emails, but cannot accept to receive unwanted phone calls or SMS; second I still consider my phone number a very personal data, unlike the email address. To give you an example, I didn’t link my phone number to Twitter because I still feel that I need to keep my real and virtual lives separated. My feeling is that a lot of people still feel the same way, but maybe you have some numbers that prove the opposite.

Another topic is that sending out validation emails is easy and free, while verifying phone numbers is costly (and can be expensive and unreliable if you have an international audience) and requires 3rd party integrations.

If it was my project, I would go for a social login. This anyway doesn’t necessarily solve the problem of how difficult it is login from a mobile, just gives the responsibility to a 3rd party (might it be google, or Facebook, or twitter). On the other side, if you delegate login and data gathering to a 3rd party then you lose the possibility to make money on top of your users’ accounts, unless you ask them to voluntarily disclose additional data, but then you saved them a login form, just to serve them with the usual big form.

In conclusion, I think that the title of this article is a little bit misleading, since it talks about login/signup strategy not necessarily related to mobile platforms.