Academic Writing and Plagiarism

So far I've taken classes in a few different subject areas and have experienced a wide variety to Academic writing.  Although all types of academic writing strive to make an arguement or prove a point the styles of writing are different. College level writing involves a lot of thought.  It's a careful process because you have to manage to tie in the ideas of different authors or researchers without stealing from them.

The hardest thing, for me, about Academic writing is making sure my ideas haven't been used by someone else.  In all honesty I don't understand what the goal of academic writing is.  There have been times in some classes that I've attempted to tie together sources to showcase an idea that I (thought) I created, only to have a professor write "site this!"  I get nervous because I feel like everytime I write a paper I need to do incredible amounts of research to make sure nobody has said the exact same thing that I'm saying without me siting them.  It really reminds me of the Harper's Magazine article in that way.  I completely agree with the idea that every idea I have is technically plagiarized from someone else. 

On a slightly different note I feel like this blurred line of what we can easily site and what is almost impossible to avoid "stealing" is a central problem with a lot of the internet banning bills.  We want to avoid plagiarism yes, but where do we draw the line between "stealing" and "creating?"