This Scam potentially give the scammers a way to get access to your Google+ account. Since it is a way that Google uses to identify you if you loose or forget your password.
Assume for at moment you forget your password for Google+ or gmail. Google will send a message to your phone (Android phone) requesting saying that there is a request to reset your Google/gmail password. You simply answer yes or no to the question and you get a new password. You see the potential dangers to hack your email account.
A sophisticated phone hacker can hijack your phone number for at least a short time... So this should be waring not keep sensitive information in your email account.
Additionally if one day you cannot login into your gmail account and you have to reset your gmail account it probably means the account was hacked