If you do a Trulia search using the search box to the left of your screen..., for cancel listing or similar you will find that there are about 13 similar questions with over 60 responses.., which may help.
I would give Ian a thumbs up for best answer on this one, as seen below. My take on it is that a lot of sellers blame their Real Estate Agent if and when their home does not sell.... its just human nature I guess, but is it fair? That depends on what the whole story is. I believe most agents try to do a great job, otherwise they will not stay in business very long. - That being said, we have seen some sellers go through 4 or 5 agents and only listing with them for 2 or 3 months thinking that ONE of them MUST have a buyer in their pocket or will "DO" something different.
Fact is that about 95% of homes are sold from MLS Listings and by licensed agents working with a buyer. If you have a sign out front, a flyer box with flyers in it (hint) and a listing on the MLS... you have what most agencies will offer.
Its a tough market out there for some folks. When you change agents or brokers you also loose momentum and market sharpness, it will dull or dampen your sale IMHO to be jumping from agent to agent. Even the public begins to wonder "what is wrong with her property that it has been listed by so many agents...?" The better tactic is to look at what is holding back the sale in real time, is it the curb appeal or maybe just the price is not in line with what the current market conditions are. We find many homes that are really worth a lot more, but just will not sell until they come down in price. NOT what most people want to hear. Those of us who invest are in the same boat with you... sometimes we have different ways to deal with the market than most average sellers. Patience.
Best of luck,