In a mediated world, assumptions and norms about the visibility and spread of expressions must be questioned. Many of the most popular genres of social media are designed to encourage participants to spread information.
I agree with this statement, especially the first part. People make different assumptions and this is where we run into problems online. People have different lifestyles, customs, cultures, and world views so they don't always see eye-to-eye and it causes tension. We need a more unified set of norms so that people don't run into problems.