There have been many, many letters that I ignore because they don't include a salary range. By not being open about it from the beginning, I become inherently suspicious of any offer given. Not only that, but if a range is not given and they offer me less than what I'm making now, I'll be pissed as I just wasted a day or more going through this process.
Also, if I don't know who the company is, I immediately decline. There are certain companies and industries which I am morally opposed to, and if the company believes so strongly that they cannot reveal themselves then the first question that comes to mind is "what is the mystery company doing so bad that they are afraid to let potential candidates know their name?"