Is implementing dark patterns unethical?

A recent question and discussion got me thinking - some UX practices are considered "dark patterns", and they're held up as bad UX from the user's perspective, though they can actually be good for the person implementing the design. There's clearly a conflict of interest here; some people would consider them "unethical" and refuse to use them. Others may not agree, or care.

Is implementing dark patterns really unethical behaviour? Why? And what other behaviours do people believe should be avoided - is neuromarketing unethical? Is it unethical to make a user experience too slick and easy?

I'm aware that this question could easily slip into discussion, so it's probably best to focus on specific behaviours which could be considered ethically questionable.