It's safe to say more than just one! Most agents have houses all over the city that they’re trying to sell at any given time. This means the attention your home needs might not always be there.
Some agents will let you list your home for an inflated price just to please you and get your business. Then when it doesn't sell they suggest you lower your price to something more "reasonable" and marketable. They get your business on the front because you think you might get your price. Your interests are at risk, not theirs, while your home sits on the market unsold.
"...some unethical agents may suggest selling prices that are too high solely to obtain a listing. Instead of competing based on a professional approach, they appeal to an owner's greed." (This is an excerpt from "California Real Estate Practice", a required course for all prospective Real Estate Agents by the California Department of Real Estate.)
In their highly competitive business, agents use different sales tricks ("games") to secure a listing. Higher sales price is one of them! Watch out!
"Dirty Little Secret" - the agent's sign in your yard is a free billboard, advertising the agent’s services to the whole neighborhood!
No wonder why so many agents discount their commission to only 4% (even 3%), instead of an average 6-7%. They make less on your house (and do less work), but at the same time they get a few more listings off of your sign where they charge full 6% commissions. The longer your house sits unsold, the more free advertising they get; the more new customers they get; the more money they will make. So at the end it works great for them, but not for you!