Meanwhile things have changed, the internet became a part of every day life, but something remained the same as the times it was only in the imagination and plans of few people: the employers are always asking for references. Long, long time ago, when the world was in a galaxy without internet, the old fashion way as to phone the previous employer and ask him (or her) about how kind of people was the employee wanabe. Lately the job of asking references has became a lot more easier: it's enough to search and browse the guy's social network accounts.
The quality and the quantity of people's tweets can be a good judge for the one who's writing or sharing them. Some people made history with what they said, in bad and good ways... and they are or were remember for that: something written in a moment of stupidy or rage can follow the writer for the rest of his life. On the other hand, almost no employer will be interested in someone that's loosing his time tweeting instead of doing the job he is hired to do. More, nobody will be interested in someone foolish, who speaks or writes stupid things or, at least, nothing of values.
Some people say that a man's destiny is written in stars. I am telling you that your destiny can also be written on twitter. Tweeting can make you popular, but being popular is not always something good: you can lose some things as you gain anothers. As mentioned before, managing your time and followers can be an expensive thing in matter of time and energy. If you do it in your free time it's OK, everyone is entitle to entertain themselves as they like. But if you do it while job time, without your employer's approval or knowledge (for some people social media is in job description), it means more money than you deserve for your work... and your boss won't like it. You can be fired for something like this...
As a conclusion, nobody likes to be associated with peopla having a bad reputation. Tweeting stupind and bad things can bring you bad reputation. Remember that when you fill in and send to the world your resume or when you write on twitter (or facebook or any other social network) that you are employeed to some company you become a representative of your employer (online or offline). People have the tendency to associate your employer to you when something bad or wrong is happening - it's not nice, but that's how the world is working.
So be careful, whatever you in the online stays forver on the internet... no matter if you see it or not.