Who's the real listing Agent?

Many people get confused when they call up a real estate agent and later find out that agent is not the sales person or listing agent for the property. This is just one aspect of this complicated business. Another scenario that is confusing is the open house. Sometimes you go into a home an agent shows you around but as you leave you notice that the picture on the for sale sign totally does not match the agent that just showed the home.
For most home buyers, none of this matters because what you are really interested in is the home. But for people that strictly want to deal with the listing agent, I think there's no better way to find out who you are dealing with than asking the agent yourself. Again, why does it matter? Well, some people have the impression that by working with the listing agent will save money by taking out one middle person. What is not commonly thought about is the contract that the listing agent has in place should the Buyer be introduced by the listing agent. Essentially the listing agent double ends the deal and gets the buyer commission for their work on finding the buyer. So the question is, has the buyer actually saved any money?
Personally, I think it would be difficult ethically to work for both buyer and seller when it comes down to negotiating the deal. The agent is built a trusting relationship to both sides and so how do you argue for a better deal? Who are you arguing for and as an agent keep impartial? Can you as a seller or home buyer trust the agent without a doubt, to not reveal what is deemed confidential during the negotiation process since they are working directly with the other side?