I agree with clane, newspeak is the government's tool to limit the people's range of thought, and to control the masses. By systematically reducing words and eliminating language that is potentially subversive, they can eventually dumb their society down so much that people won't even be able to think or to formulate words of resistance. According to Kenneth Burke, the terms we choose not only reflect, but also select and deflect reality. By controlling the terms, the government also controls the values connected to those terms, as well as the emotion. Newspeak, like the content of the news, is nothing more than a series of spliced segments of meaning. Newspeak is the ultimate reflection of a reality devoid of meaning.
The government in 1984 employs people to help create a language, which really isn't creation at all, but the destruction of words. The purpose of destroying words is to limit the thought and the range of thought of this society's members. The purpose of limiting the thoughts of the society is that with a smaller range of thought, the members will be easier to control. The society will no longer have limitless ways in which to express themselves, there eventually will be a fixed amount of ways in which one can express only the very basic feelings one has. "Newspeak" is the government's just one more way that it can truly possess its society members.
The government of Oceana would use this for several reasons. First, they are trying to create something new: a new language that shapes thought. Second, they are giving that language a name that reflects its principles: creation, forcing and shaping thoughts, etc. Third, they are trying to grab some of the allure of the news; to speak in this new society is to take part in creating the new, and the news (blogs, anyone?). Fourth, to drive out old languages like the English we use.