Is Twitter a social media or a social game?

Twitter announced that it has already have 175 million accounts by May, 2011. Although according to some reports, the active user number is about 85 million, it is a huge number and more people treat twitter as one part of their lives. People not only use twitter to follow celebrities as well as friends, but also use it to let the WORLD know what they are doing, e.g. what restaurants they are going, what thoughts they have etc. A question come to my mind, is Twitter really a social media website, that people use it to gather information/build up relationship, or it is also something else? I found it interesting that Twitter also looks like a social game to me. Different people use it differently. It is just like you are playing a role in the twitter game, you are playing a "twittered you" online. You decide what kind of information you want to twitter. Because people can not twitter every aspect of the their life online, they choose what they want to say and what kind of image they want to show to others. Although these information is true, I would say there is still a sense of acting in the twittering behavior. Someone always twitter what books they read. They maybe are true book-lovers, but it is also possible that they want to establish themselves as book-lovers. It is just like playing a game. Just my two cents here after I heard my friend said that is easy to find out what kind of person a people is from his/her twitter account.