I tested this fairly extensively a couple of years ago. Some major search engines did bump you up with no other change than going from eg: geocities.com/chair-design.html to chair-design.com. I had intended to also test it with 3LD's but never got around to it as the cost of an SLD with the keyword(s) was insignificant.|
I have no doubt that it was more than superstition, some engines did give weight to the keyword in the SLD of the URL, I believe there are still a few that assign it some weight, though that number is lessening all the time, as I say the current model is to charge for better placement, or in altavista's case, to charge you to get listed expeditiously instead of a few months later. I realize search engines have to do this to stay alive financially.
OTOH, their relevance goes down in many cases, site money available does not necessarily equate with site usefulness, so users cease using those search engine. Altavista is again a case in point, their hits have dropped in inverse proportion to Google's gain. Those who think that money can fuel or guide the flow of electrons will continue to be baffled by why that model just doesn't work online. You could call it failure to grasp the concept. -g