It's impossible to over-emphasize the importance during salary negotiations for neither side to capitulate. Neither the employer nor the candidate should ever feel as if they've been put in a position to make concessions that aren't mutually beneficial to their aims.
If a job candidate is too desperate to reach an agreement and yields to the employer's final offer with any feelings of having been taken advantage of, or of being undervalued, this can play havoc on their attitude toward the job.
Likewise, an employer has to weigh their need for a particular candidate against their financial ability to make them happy. Agreeing to a salary that can't be afforded is the first step on the road to ruin.
In the end, both should be satisfied with the agreement. Having a recruiter as the middle man in these final negotiations removes some of that risk, and alleviates most of the stress involved in intense salary negotiations.