Alright dudes, hopefully we're all adults here and can hold a sensible discussion about this stuff. Firstly I gotta say that I don't believe that subliminal messages are an ethical form of marketing, that is, even if they carry the power that some would have us believe. Here's a details of an experiment that showed a 41% traffic increase to a target page by using a subliminal. I don't condone the use of them and conducted this just to see if it was possible. http://mickmeaney.com/subliminal-advertising-works-well-kinda.html I thought the experiment would produce nothing, but there's so many factors to consider as to why this worked.. and I don't regard this as any form of conclusive evidence.. it's just "interesting", at least to me.
One of my focuses in my day job is increasing conversion rates. There are a lot of little nudges that can be done including showing some security symbol, changing the color or wording of the add to cart button, reorganizing product categories, etc. If subliminal messages nudge people along I don't know that it's unethical, nudging and closing is called selling. If you do something unethical with it than yes it is unethical. I am more bothered by advertising that is not true such as an automaker like Honda claiming to be the most reliable back in the eighties and early nineties while I consistently counted about 50% of the broken down cars I saw had the Honda/Acura/Sterling brand, only their breakdowns were reliable. If you are subliminally moving your visitors through your site with a message, how is that different than moving them along aided by a CNN level web design while you are just some guy with a blog.