They do it very often. The smaller firms are better but you have to realise these recruitment consultants are sales folks, they don't give a damn about you or your career, all they care for are their targets and their commission.
Not to be sexist but they preferentially hire women (you'll find online that women are far more effective salespersons) who speak well and most of these women will talk to you as if you mean the world to them and will not give an eff once the next candidate comes around.
Hell, one lady would call me everyday and send me messages like "Hey, I only want good things for you, you deserve the best, you are so sweet" etc and my friend calls me to tell me that she approached him for the same role which she had been promising to me was in my pocket.