Should people use "FACEBOOK"???

Thanks to the technology today, so that people can make net pals, meet friends, find colleagues, keep in touch with friends all over the world by using many different find-people websites, such as, facebook, WYAN, Targeted, HI5 and many others. But how security are these websites? Can all these create a personl profile online to public bring any disadvantages to us or damage our future career?
A true story about some people created online profiles leading they getting fired by the company. How did this happen? And what did this has to do with people having a profile just in order to make internet friends?
The reason behind this was a person who in charge of hiring employees of a company, found out his/her employees' internet profiles containing alcohol abusing at pubs or clubs, sending naughty messages to his/her friends, and telling the public that he or she is a gay or a lesbian. This hiring person automatically thinks employees behave like this will influence others by their messy private life, and will bring negative impact to the company. This kind of assume is especially happening to the Airlines because the airlines' employees represent the company, and happening to the school because parents will preserve sexual abuse on children if this teacher is a gay or a lesbian.
Yes! People argue that a person's private life should have nothing to do with their jobs, and having a horrible life after work doesn't mean that they do not perform well at work.
Yes! Indeed, people think companies should hire by skills not by the personality or should hire by personality or skills. However, companies can always make up unreasonable excuses just to fire you in order to save more labor costs.
As long as you are the owner, you have the right to choose what kind of people you want to hire, such as religions, skin colors, politic preferences, nationalities, beliefs and so on. Also, some diseases or illness can be a excuse for owners not to hire you.
The story above explained why these people got fired, simply because their owner think naughty or discrimination messages they send to other colleagues had already proved they are discriminal to others. Does this discriminal issue need to be proved again? No, it had automatically been proved by the public or others without any checking to done by the owner.
And it gives the owner a great excuse to dismissal workers just to save more money.