https://www.vice.com/en_us/article/9kez8d/twitter-took-phone-numbers-for-security-used-for-advertising > When some users provided Twitter with their phone number to make their account more secure, the company used this information for advertising purposes, according to a blog post from Twitter published on Tuesday. > This isn't the first time that a large social network has taken information explicitly meant for the purposes of security, and then quietly or accidentally use it for something else entirely. Facebook did something similar with phone numbers provided by users for two-factor authentication, the company confirmed last year.