I always assume that job postings that don't list a salary are sketchy. It's like going to a store and seeing "Make an offer" on the price sticker. I remember when my boyfriend was working at an early version of Best Buy, and foreign shoppers would come in and try to dicker on the prices. We used to laugh at that. We thought it was so funny! That was a long time ago.
Requiring the applicant to give a salary is a not-very-subtle signal that you are targeting your ad to people who are culturally conditioned to dicker for everything. In other words, "Americans need not apply".
This message is not really intended for JoeInBallard, since he knows what he is doing - it is more targetted to people who read the posting, and fell uncomfortable, but don't know why. It took me a few minutes to be able to identify my discomfort, and I decided to post that recognition.