Aside from the technical aspects of a sale and the mistakes people can make in the paperwork, real estate agents know neighborhoods and houses inside and out.
Mendenhall calls it the "purple room" phenomenon. If a buyer wants a house with a purple room, she says, the experienced real estate agent will know the house that's for sale that has that room.
In a more general way, an agent will be aware of features that don't show as well on the Internet. If a buyer is looking for a house with a space that could be used as an office, an attached mother-in-law unit or a room that's perfect for showing off a prized grandfather clock, a human agent is more likely to find a match than a real estate Web site.