My mother (and many many women in this modern world) _goes by her maiden name_ so it's not exactly a secret.

I always (politely) point this out when I'm dealing with a human at an institution who asks me for this information as part of the security process.

Even when a woman does change her last name after marriage, believing that her maiden name is somehow secret information in this day and age seems about as secure as "what street did you grow up on?", or "what was your high school mascot?". The root of the problem is believing that security questions are a good practice to begin with.

On top of that we are living in the era of social media, where these type of information are no longer hard to find.

Yep, plus all the people who don't live in a culture where "maiden name" implies anything.

Good point.