I guess that's what the platform.qbix.com app is set up with. Q apps can be configured out of the box to let people sign up using email, mobile, or facebook. You can also code your own adapter (such as using some other OAuth) and if you do, contribute it to the community.

I should mention that the main reason "mobile only" is the default is to try to prevent sybil attacks ... if you're a startup looking to launch an app, the last thing you want is to have some jokers create a million accounts and overload your site with inane stuff. Q expects that you'll require an authenticated session id for most of the "expensive" stuff like realtime pushes, notifications, or whatever your app wants to implement. But if people can sign up with 1 million fake emails, that won't do much good. It's hard to make it expensive to create hundreds of accounts and requiring a cellphone number is the only way I know, aside from requiring valid billable credit card numbers. Facebook commect MAY be a close second.

Also, people tend to pay more attention to SMSes which improves your retention until they download the native app and switch to in-app notifications. (You alluded to this by saying you got a lot of SPAM... that's why Q always has a way for users to unsubscribe.)