Something you're reading that doesn't seem as good as it should because you feel imaginary eyes behind you saying, "make a claim for that, justify it." Or writing academic prose and feeling an imaginary reader responding, objecting to your argument. That imaginary reader is always some specific person; for example being told who the respondent is for an MLA session I am on. Now, when I write the paper, I'm thinking how that person will respond. Not exactly liberating.