Emma Thompson is unhappy about the way language is used, particularly by young people. Read about it here.
I think it's only fair to take a balanced view. Personally, I adapt not only my language but my accent depending upon who it is I am speaking to. My reasoning here is simple: I communicate in order to be understood. Consequently, I do whatever I feel is necessary and within my powers to achieve that. So, if I'm speaking to friends from the north east of England, my accent is likely to be more pronounced than if I am speaking to people from elsewhere, and if I am chatting to friends, the language I use will be far less formal than if I am chatting to someone in a business context. It's the same with texts and emails. I think probably the majority of people do the same, but do it instinctively. It's all about getting it across, irrespective of whether the words are written or spoken.