Don't count on it. Unless you have a written Agency Agreement, the Law of Agency, as defined by federal and state courts, specifies the contractual relationships that are formed when property is bought and sold. Agents listing property enter into a signed contract with the sellers to represent them in the sale of their property. This same contract permits the listing agent to use "sub-agents" to help secure a sale. 

Unless you have a written Agency Agreement with a real estate agent promising to represent YOUR best interest, the agent showing you homes should be considered a sub-agent working for the seller.