Headhunter ads posted on sites like Dice and Monster annoy me. The headhunters (they like to be called "recruiters" from "staffing agencies") are serving no purpose. So far, the only purpose I know for a headhunter is to serve as a human search engine matching resume key words with job description key words, but if I'm already using the Dice or Monster search engine then I have no need for the headhunter. When I see these ads, if I can I try to figure out the real company with a Google search on some unique phrase in the job description, so I can go to its web site and apply directly to the original version of the job posting.
If I get desperate, I may try using a headhunter if they actually tell me about a decent job, to reward them for being a good search engine, but once I know the name of the company I will give them some limited amount of time to get me an interview. If they don't then I will assume they are just screwing with me and will send in my resume myself (which is what I would prefer anyway).
I respect companies that post their own job openings. Headhunters just get in my way, ask me to describe in detail my technical experience when they are incapable of understanding it, and misinterpret basic things about the description of the job they are trying to force on me. How can a "recruiter" "recruit" when I can understand the job description better than they can? I'm recruiting myself!