Is pronunciation as important as it used to be?
My observation is that there is a trend in the internet that some people, especially the youths, intentionally alter the "Han Zi" expression of some frequently used words. It is a way they make fun of their text and want to be more attractive.

The reason is not because the tone in the language is less important or has any change. It is simply a technical issue. Most of the PinYin input systems in computers and smart phones do not request a tone input. Instead, the screen may display a list of homophones to choose. This provides a chance for the youths to play with different characters. 

While most of the "experiments" are wrong, a few of them indeed makes sense. For example, "什么都是浮云" （什么金银财宝对于人生来讲，都是过眼烟云，不值一提）was changed to "神马都是浮云". It has an apparent meaning that the shape of a horse in the sky is actually cloud. But the readers still are able to connect it to its original meaning.