I found the following bouncing on the web, and I think it’s worth to share it.
The idea of authors being “unethical” is often used when it comes to self-publishers and independents.
The sum of all that’s wrong in publishing, self-publishers are said to be sloppy, poorly edited (if edited at all), greedy (selling short stories at high prices), unprofessional and, when everything else fails, unethical.

And granted, there’s people like that around.
But that does not mean that everybody’s like that.

So, here’s a simple set of rules.
The fact that it’s been necessary to put them in writing – when they should be obvious and natural – is sad, but as the guy said, better safe than sorry.
(click to enlarge)