I've been reading many posts about Open Houses, I can see why they might not be effective in many markets.
In Manhattan we do not have lock boxes or keys available to show a property. In Manhattan the listing agent is almost always present during a showing. An appointment has to be made with the Listing agent at least 24 hours in advance to show a property. Scheduling appointments for buyers is one of the most difficult tasks we have as buyers agents in Manhattan. When working with buyers we are at the mercy of the listing agents time. Setting up itineraries for a buyer is very difficult. Many agents do not always return phone calls or answer emails. But they all do Open Houses. Sometimes an Open House is the only opportunity I have to show that property to my buyer.
Sometimes I have to show up at the Open House with my buyer after fruitless attempts to get an appointment. If my buyers are interested we leave and discuss a strategy. I often go back to the Open House by myself and feel the agent out. I always like to talk to the agent first before I make the offer.
I must admit there is a whole new attitude since the market has cooled. Agents with buyers are more popular these days.
I can usually show a buyer every property in their price range and neighborhood in a few hours on a Sunday. Make offers that afternoon and the negotiations take place during the week.
For sellers they don't have to be kicked out of their house every minute. By having an Open House many buyers can see the property in a short period of time. Often offers are made right on the spot at Open Houses.