Even if "The challenge question are based on personal information" it doesn't mean you have to answer them as such.
There are many simple tricks to make it more difficult to guess passwords, eg start always with a certain character, repeat words more than once, add an offset to a number, etc. I am sure you can think of some easy things yourself. But rule number one is "never do what other people expect".
I'm on Facebook. I've *never* considered it secure. My profile is deliberately minimal. I assume everything I post will be accessible, regardless of privacy settings, so I only post things I want everyone to see.
But I may remember to actually check Facebook once a week or so, and if my account went away, I wouldn't miss it.
An old friend in publishing popped up on Facebook, and I said "Welcome to the infinite time sink". If I want to waste time, I can think of few places better suited for it. If I want to actually accomplish anything useful and productive, the opposite is true.
While an awful lot of people I know on are on Facebook, Facebook isn't how I communicate with them. I have no interest in online games, and I don't particularly *care* what someone just had for lunch.
Nothing that I might do professionally is in any way enabled or enhanced by Facebook. Very little of what I do personally is either.
I advise against joining Facebook because the time you will spend on Facebook is time you almost certainly *should* be spending doing something else.
The tool is out there and it is your choice of how you would like to use it. Signing up facebook doesn't automatically mean revealing your personal information. There are various privacy settings available. Ultimately, you can choose what to post and what not. Facebook or any social media is a good way to connect to your friends and, share your photos and status with them. I keep reminding myself it is not a online diary and notepad.
I joined Facebook a year ago in order to be able to get access to my new grandchild's photos. While I LOVE the photos, I have come to regret joining Facebook! Constant emails to friend someone, birthday notifications, someone has tagged you in a photo. If only I could delete it completely... never again. It is such a waste of time!
I'd like to point another possible reason for NOT exposing yourself to the world in a medium not under your control. The fact that we have to be popular in order to succeed and "like" things, ideas, actions, and thoughts just desensitizes us as a society. I can understand that as a marketing tool for goods, services and careers social networks can be useful. But for personal matters it robs us of our individuality in favor of becoming just another blob on the mountain of irrelevancy. I offer the following essay for contemplation: http://www.cnn.com/2012/05/30/tech/keen-technology-facebook-privacy/index.html?hpt=hp_c1
Even the ancient Romans knew that "in medio stat virtus." The problem with security is, as usual, misuse of a resource.
Why so many people feel the urge to blab all their personal info on Facebook might be a good article in itself. Fighting against that compulsion should be easy enough, for anyone who really cares about these things. And then Facebook would be no problem.
Google itself has already been hacked at least once. Do you really think your personal data is safe out there in the cloud somewhere just because you clicked some facebook privacy buttons? The only reason your personal business is not already public or worse is because the Chinese red army doesn't care about your mothers maiden name. But sooner or later, facebook will be compromised just like Google, the U.S. military network, and all the other systems that have already been compromised. These systems are fallible, made by fallible people, and are irresistible targets to evil-doers. Unless you think that the next security update will be the very last one ever needed, you should probably make your peace with your inner paranoia.