Sometimes it may not always be that obvious why people join social networks around the world. The reason varies from person to person but usually they fall into one of the next few categories.
A good reason most people join social networks is because they want to make new friends. Social networks expose people to new people from all around the world and out of all of those people there is a good chance there will be new friendships made. People will find other people who have similar interests as them and begin friendships with them, this is one of the more basic reasons for joining social networks.
Another reason why people join social networks is to show off their talents or knowledge. Since most social networks allow people to show off who they are and what they believe in many people take this chance to show the world what they can do. Whether it is special abilities such as writing, art, music, whatever, people enjoy having thousands of potential audience members at their finger tips and take advantage of it by broadcasting their talents to whoever willing to notice, in this way they feel they may get the appreciation they deserve from people.
The third reason most people join social networks is for work related purposes, people use social networks as a way to find jobs and hire employees. Certain professions such as writing make very good use of social networking to find people like themselves who have a passion for what they like to do. In this way they can share information about the business and what the current trends are. Also employers seem to be screening people more and more through social networks such as Myspace which may or may not be a good thing depending on which perspective you look at it from. The employers are seeing many potential employees for what they really are on these social networks which can make or break a potential job offer.