android password or phone number to sign in

I created this question to gather information only.

I just read about the phone WhatsApp and Viber chat applications and notice it using

the phone number to sign the user in.

This is really good as for user experience not 开发者_运维百科have to remember passwords or usernames.

The question is the good/bad comparing against the password/username.

What are the good and bad of using only the phone number?

Can user login using anything else then he's phone (pc,tab)?, restrictions?

Is this the future preferred way?

Not having a username feels like a restriction since there's no easy way to search like in facebook

Would appreciate anyone with experience of both approaches to say something.

I have not witnessed any apps that use this a login model. But it seems as thought it would alienate any wifi only tablets from being able to use the app. The tablets with 3g/4g on them that I have seen are able to receive SMS and thus have a phone number, so those ones would theoretically still work.

As a user I would not like this model at all. I would view it as nothing but an attempt for them to get my phone number in order to send me txt's that I do not want, or to sell said number to someone else who will send me txt's or cold calls that I do not want. I would way prefer the username/password style login. So much so that I would probably just uninstall an app if it asked me to log in that way.

Edit:

"All app's you install on the phone have access to your phone number and all your email addresses"

-No they do not. Both of these items require permissions to lookup.

AccountManger.getAccountsByType(String type)

This method requires the caller to hold the permission GET_ACCOUNTS.

TelephonyManager.getLine1Number()

Requires Permission: READ_PHONE_STATE