Why do some people on the Internet insist on using acronyms and making spelling mistakes?
Besides the great answers that have already been said, there’s a sort of escapism that can be associated with the Internet. The Internet is a different world, with its own friendships, its own way of defining your image (e.g., the colors you use when you type or the background on your MySpace), and perhaps even its own take on language. Internet acronyms were more commonplace with a more diverse group of people back when not everybody had the Internet. Acronyms and shorthand spelling were a way of being quick to keep up with the chatroom. Some people chose to cling onto that, and others decided the Internet was primarily for something else.
