|Pure hearts and empty heads.|
There is one limitation to the innocent intent is no defense to copyright infringement statement. YouTube, and other internet services providers, are shielded from secondary liability on the condition they remove infringing content posted by users when notified of the infringement by the copyright owner.
While not a defense, intent is relevant for purposes of determining damages. Bad-faith infringers are treated more harshly than innocent ones. One point of view is the deliberate affixing of a "No Copyright Infringement Intended" disclaimer is evidence that the person either knew they were infringing, or recklessly disregarded the possibility. Unless the poster has entered the no-man's land of fair use, where there's refuge in the interstices of the law, it's self-incriminating behavior. In other words, a naive bluff calculated to mask the user's bad intent to reproduce a valuable original, not create something new that stands on its own two feet.
By broadcasting that the risk was either known, or somewhat likely, what is designed to dampen risk, can, in fact, raise, rather than lower, damages. In cases where the infringement is willful, depending upon the degree of culpability, a court can award between $750 and $150,000 per infringement, plus reasonable attorney's fees and costs. This is known as statutory damages in copyright jargon.
When Mark Twain was accused of cribbing the dedication to his ironically titled The Innocents Abroad from a book of poems by Oliver Wendell Holmes, he quipped, "Adam was the only man who, when he said a good thing, knew that nobody had said it before him.” Twain's point, or purpose, wasn't forgiveness. He was driving home the point that his behavior was neither good nor bad. His subconscious was to blame. While mildly unrepentant, the explanation makes Twain appear less blameworthy than if he included a "No Copyright Infringement Intended" disclaimer on the reverse title page of his book, or delivered an apology that appeared insincere.
What was true for Twain, was also true for Holmes, who reportedly laughed off the incident, saying there was no crime in unconscious plagiarism, which he said, "I commit everyday."
ResourcesFitzgerald Pub. Co., Inc. v. Baylor Pub. Co., Inc., 807 F. 2d 1110 - Court of Appeals, 2nd Circuit 1986
ABKCO Music, Inc. v. Harrisongs Music, Ltd., 722 F. 2d 988 - Court of Appeals, 2nd Circuit 1983