The point is, you are powerful. you are shaping the Internet, leaving a legacy that will echo for years to come. Whether you organize a big campaign to combat issues of online incivility, actively stand up against cyberbullying or just lead the way by modeling ethical online behavior, you can have a real, lasting impact.
My opinion is that there are many things that you can do that can hurt people really bad and also it will stay on the internet.
My favorite passage is "No book can tell you how to be a "good" person. Life has too many gray areas. And the internet presents even more."