In many real estate markets some listing agents think they are clever advertising ‘pre-listings', or the latest one I've seen on some yard signs as a rider that says "coming soon!"  Upon further investigation, you'll find these listings are not entered into the MLS system.  Under most state real estate license boards it is illegal to advertise a property for sale where the listing agreement has not yet been signed. Implied representation is deceptive and fraudulent.  For most Realtors® and MLS board members there is an agreement and understanding that all participating brokers will place all their listings into the MLS systems, and do so within a predetermined time-frame which is usually 24-48 hours.  The reasoning is obvious; the listing agent will have an unfair advantage in having a listing all to themselves when the listing agreement is predicated on an exclusive right to sell MLS agreement where all members will have an opportunity to sell the listing.  Such behavior is referred to as "Pocketing the listing!"  Such behavior should be cracked down by the principal broker, and the behavior is totally unethical, and most probably illegal.