From https://www.wired.co.uk/article/personal-da...acebook-twitter

"The internet can be an obnoxious place, and the sharing culture of social media often runs counter to security and privacy best practices. Most of us have at some point shared our birthdays, photos of our loved ones, information about where we live and come from, and other content that perhaps shouldn’t be made public online.

In a worst case scenario, information you share online could be taken advantage of to pose a threat to your security or even physical safety. The fundamentals of securing your online presence are much the same regardless of what online services you use.

Before we get on to specific actions for Twitter, Facebook and LinkedIn here’s what you should be aware of if you’re looking to better protect yourself online and make sure your information has a smaller chance of being abused."

I like the name of the article you linked, "The Ashley Madison hack proves it: Everyone lies about their birthdays.“
It's a good point. When sign up for websites, use some fake information like fake birthday, fake last name and it might make extra protection. Of course, when your mother says Happy Birthday on Facebook on your real birthday, maybe the secret is out.