How does adding a personal phone number to a Google, Yahoo or Facebook account make it more secure?

[NUNYA B]

Both Google and Facebook and Yahoo keep pressuring me to add my phone number to make my account more "secure". Seems like putting ones personal phone number on an internet profile account would actually be more of a security RISK allowing access to illegitimate billing and irritating telemarketing.

[abraXus]

it's so that if your account gets "hacked" you can recover it using your phone

[Champ]

If you ever forget your password, or your account gets hacked, and if you have entered your mobile number, they will send you a message containing a code and if you enter that code you can get access to your account. It is just a way of confirming your identity and keeping your account secure. Besides, if you enter your mobile number, you will also get important notifications, login notifications, etc if you want.

[Old]

If someone steals your phone,, you can forget ever being able to get back into your account. Now they have access to your Google and Facebook and other information.

Anyone storing personal info with access to accounts. shopping online, or downloading apps, on a phone that can can be easily MISPLACED, LOST or STOLEN, is not wise at all.
So NO it is not more "SECURE" it's just more convenient.