I recently read a question on Yahoo! Answers about someone being asked what their mother's maiden name is. Of course this is a huge risk. Never divulge your mother's maiden name! That's a direct threat to the protection of your identity.
To quote the person asking the question:
A woman sharing my last name has contacted me on facebook about family tree research and I would love to help her out. She is just asking the names of my Parents and Grandparents. I complied and she responded asking the maiden names of my MOTHER and GRANDMOTHER. This is strange because the side of lineage she is researching is the side of my FATHER and GRANDFATHER.
Yes it is strange - or maybe not so strange! This is exactly what the scammers do to steal your identity. They know the woman's name and many of her other personal details from Facebook. They can probably do a fair bit of damage with just these, but if they get her mother's maiden name as well, then there's no telling what they'll be able to access.
Think about it. How many services out there are there that ask for your mother's maiden name as a security question?
The obvious ones are the banks. Many bank accounts have mother's maiden name as a security question. If you call the bank, or use Internet Banking or even have a problem with the signature, one of the questions they'll ask you is this. It won't be enough by itself for scammers to get access to your accounts, but they're halfway there, and if they play their card's right, they may be able to get access to your bank account.
Of course there are many online services which ask you for your mother's maiden name as part of their "forgot your password" functionality. These days there is trend against using mother's maiden name, precisely because it got to the point that this was used by many services and became a target of scammers as a result.
The new model that many online services use, allows you to choose your own question and answer, to avoid this problem - however, you would be surprised how many people still use their mother's maiden name as the question and answer!
It's hard-wired into our brains now as the security reset question, so many people choose to use it, unaware that their identity is at risk of being stolen.
This means it's still worth the scammers' while to try to get your mother's maiden name. Like email spammers, it's a percentage thing. If they try enough people, they'll find one who's using mother's maiden name as their security question.
Now, imagine what would happen if someone got control of your email account. They could effectively become you. Not only do they have all the information you have in your inbox, they can organise for many things to happen. These days email is treated as being almost equivalent to signed requests in writing.
Just sticking to the internet, a subject close to my heart, many websites which get hacked through their email account. The hackers steal the website owner's email address, then use it to contact the website's hosting service and change control of the website to themselves.
In the wider world, there are many other things that could be done. Just imagine it!
Now, think about identity protection and protect your mother's maiden name like it's gold!