I felt very uncomfortable having someone negotiate on my behalf. Although X was capable and acted in my interests, I would not have been satisfied with anyone or any outcome that wasn't exorbitantly in my favor. I've always believed in "if you need a job to be done, you had better do it yourself."
The trouble is, in order to survive (much less thrive) as a business person, doing everything yourself will soon prevent you from expanding your scope. To stretch your span of operation--and therefore your influence or your profit-- you have to delegate work to many others--fraught with risk though that can be.
1. Everyone needs negotiation agents; conversely, almost everyone IS a negotiation agent. Anyone who has permission to make decisions on behalf of others is an agent. In a corporate setting, for instance, your company's lawyers are obviously agents, but so is the assistant who negotiates prices on office supplies, the personnel department who hires your staff, the retail clerk who gives a customer a discount, the security guard who judges who should be let in the door, the facilities manager who locates office space, the systems analyst who customizes software for use company-wide, the engineer who is collaborating on a cross-industry research project.....and on and on.
2. Therefore, understanding your position as an agent and your position as a client is essential to successful business negotiations--from buying paper clips to pulling off mega-mergers.
3. Some agent relationships are informal, such when a colleague tries to arrange a job interview for you, or your sister when she intervenes with your parents to plead your case. With these folks, it is important to notice that you are entering an agent/client situation. This reminds you to communicate explicitly in advance about key information, your strategy and goals, what you are comfortable with having them do, etc.
4. Legal and ethical responsibilities. Negotiating agents who formally represent a client are governed by laws, contracts, and societal expectations. These agents are legally obligated to protect the best interests of their clients at all times. This can be difficult when the agent's own interests conflict with the client's.
5. Any time agents are involved, think of it as a multi-party negotiation: Despite an agent's obligations, it is wise to acknowledge that they do have interests that diverge from their clients (the lawyer who charges by the hour has some incentive to drag out litigation; the department head who is asked to fire half her staff wants to protect the good will and connections she's built up with her employees).
From an anthropological perspective, businesses and organizations rest on a foundation of social and informal agreements that people will be trusting and cooperative. There are, of course, a few aspects of business which require caution, competition, even outright suspicion, and negotiation often deals with these uncomfortable/exciting (depending on your perspective) aspects. But without trust between agent and client, effective negotiation isn't possible. This doesn't mean being naïve, it means moving carefully, gradually increasing the degree of trust/authority you give, and being trustworthy yourself.