One of the first questions we ask when working with a new client is: what tone of voice do you require when we write for you?
Some clients have never thought about this, but it makes a lot of difference. The tone can be selected to make text appear friendly, distant, formal, informal, calm or exciting. Obviously, this has a great effect on the reader.
Now, some some people think that an informal style of writing will always be more more exciting and friendly than a more formal style, but that is not always the case. Just like a hyperactive child who never stops fidgeting, an exciting, informal style can sometimes tire and exasperate the reader when over-used. On the other hand, more formal writing can appear more friendly than some people think. What is crucial is to select the style that suits your target readers. If they feel happy with it, then your writing is more likely to achieve your objective, but if they don’t feel happy with it, they probably won’t even continue reading to the end.
So formal can be fun and informal can be boring. Don’t assume that everyone finds a fast and furious tone exciting; they could actually find it boring. Choose what will work best for them.