- Nov 23, 2011
That's actually very cheap these days thanks to services like Twilio. The problem with phone number only is that it limits update and rengagement opportunity as you don't get the users emails for thread replies/conversation notifications etc.Twitter most likely has a system in place where they can send a verification text to mobiles. This must have a cost implication and would be prohibitive to a lot of forums.
It could only potentially work if there's a native app with push notifications enabled, but that's still no where to be seen. Otherwise for some sites only getting a users phone number would nuke their possible engament opporutnities for no real reason.