The “fair use argument” is just that; an argument. It’s a defense that has been used in past court cases and it is loosely defined. It is not part of any copyright law that I am aware of.

A good resource is the book, “This Business Of Music”-Krasilofsky, Shemel.

“It’s my belief (based on very little actual data) that posting a cover version of a song, not for sale, in a non-commercial way, is acceptable. Unless the copyright holder asks you to take it down, at which point you can either do that or fight them. Again, am I right about this? I don’t know.”

O.K. when you say “post” I am assuming you are talking about a digital file of a recorded performance available over the internet.

Technically, I believe, that would be considered a public release and therefore, subject to copyright laws.
This scenario also differs from the cases of Taub and Sandercoe in that, again I’m assuming, you are talking about a complete version of a song rather than just a portion.

There are a lot of people doing exactly what you’re talking about; releasing cover songs and not paying license fees. For the most part, the industry is letting it slide.

Now, if you put out the song and 2 million people downloaded it over a short period of time, you would probably be hearing from somebody.

Lucas, in his post, made the point that somebody was probably wanting to release a “for profit” version of a “Brown Sugar” instructional, that would be in competition with the YouTube one. I suspect that he is correct.
The industry takes notice when they are losing money.

Personally, I would not release a cover song for free over the internet. The nature of the digital world is that data doesn’t disappear. Over a period of time, even at a couple hundred a year, the downloads would add up and at some point the copyright owner could demand the mechanical royalty for each download.