I think they're providing this so they can make money off the information they get about users and what services they authenticate with.
It makes no sense to use SMS for a login. We know it's not secure and we know it's both slow and unreliable. As an alternative, 3rd parties can already use e-mail authentication for free. Any username/email could normally be linked in an account profile to a phone number to authenticate with, so numbers shouldn't be required for the login part. But if they use a phone number, those are globally unique and tied to a real person, and it works for people who don't have data plans.
So 3rd parties get a universal login that doesn't require a password or a data plan, they get to avoid captchas, and they get the expensive SMS transport for free. The trade-off is they hand over to Twitter who all their users are, and their users might have to wait a while to login as they try and re-try to re-send the auth token.
Hopefully they'll still support you logging in with an e-mail instead of a phone number, so you can have more than one identity for any of the services you use to auth this way (including Twitter itself).
It makes no sense to use SMS for a login. We know it's not secure and we know it's both slow and unreliable. As an alternative, 3rd parties can already use e-mail authentication for free. Any username/email could normally be linked in an account profile to a phone number to authenticate with, so numbers shouldn't be required for the login part. But if they use a phone number, those are globally unique and tied to a real person, and it works for people who don't have data plans.
So 3rd parties get a universal login that doesn't require a password or a data plan, they get to avoid captchas, and they get the expensive SMS transport for free. The trade-off is they hand over to Twitter who all their users are, and their users might have to wait a while to login as they try and re-try to re-send the auth token.
Hopefully they'll still support you logging in with an e-mail instead of a phone number, so you can have more than one identity for any of the services you use to auth this way (including Twitter itself).