Some people are chronic (compulsive, pathological) liars who lies about things for no apparent reason. No matter how small , big, unimportant or important they will keep doing it. For chronic liars, lying is a habit and everything is fair game.
When you confront them, your relationship will worsen and take a dip diving. It makes things worse. Also you don’t gain much. It is highly difficult to deal with a close one if he/she lies all the time.
There are several types (clinical) A sociopath, compulsive liar (Pathological Liar, Habitual Liar and Chronic Liar are often used to refer to a Compulsive Liar).
What I would like to focus a little here is about sociopaths. A sociopath is typically defined as someone who lies incessantly to get their way and does so with little concern for others. A sociopath is often goal-oriented (i.e., lying is focused – it is done to get one’s way). Sociopaths have little regard or respect for the rights and feelings of others. Sociopaths are often charming and charismatic, but they use their talented social skills in manipulative and self-centered ways. (This description is taken from the web)
You can read a good profile here — > http://www.mcafee.cc/Bin/sb.html
They are also called psychopaths the hard way. They are masters of manipulation. Some sociopaths (women or men) has a history of defrauding apposite gender for their gains, be it money or other benefits. It’s called love fraud. Some pay heavily once they are victims of these people be it mentally or financially.