Not all businesses allow you to post jobs to Slashdot, although I suppose I could lobby to change that internally. I'm also fully aware I need to entice people away, but if they aren't looking I can't entice them. I'm a happy employee myself, I'm not periodically checking to see if anyone has any enticing offers for me.
You're statement about narrowing my search is also part of the problem with this industry. A good engineer can work on almost anything. Hiring by keyword does not make success.