A lot of flap has been flying around the real estate industry as more and more aggregators are courting agents to place their listings on line with them. Zillow has now opened their website for listings. Point2 Agent has an interface that allows member agents to post their listings and they automatically are fed to Trulia, Google's Oodle, Edgio, and many others. Local MLS info is sent directly to REALTOR.com as well. There are so many competitors for listing info these days that it's hard to keep track of all of them.
REALTORS are discussing the possibility of a national MLS. Minnesota is working toward a statewide system currently. Agents who are members of the St. Paul MLS can view listings from the St. Cloud and Rochester MLS's. The state system currently does not allow agents to put their listings in other regional MLS systems unless the agent is a member of that system as well, but that doesn't prevent non-members from checking out their listings!
The move to integrate the different regional MLS's into a system that can be viewed by other regional members has demonstrated how difficult a national MLS would be. Different regions have different rules on how to input data into the MLS. In order for a national system to work, it would have to be identical from region to region.
A perfect example is how to list a bathroom. In St. Paul we call a bath with a toilet and sink a half bath. In other regions that kind of bath is called a 2 piece bath. A St. Paul bath with a shower, sink and toilet is a three-quarter bath. Other regions might call that a full bath or a 3 piece bath. If there is a tub with a shower head, a sink and toilet is that a 3 piece bath or a full bath? And what if there's a toilet and shower only? Or a tub and toilet only? (I've seen houses with that very problem.) Are both of those baths 2 piece?
House styles are called different things regionally as well. In Texas a one level house is called a ranch style and they seldom have basements. In St. Paul the one level home is called a rambler and it's rare for them to be without a basement. Some states are deed of trust states but Minnesota is not. Minnesota has homestead taxes but many states do not.
To bring all the regional differences into one consistent format would take a lot of hard work on the part of the programmers for a national MLS system. It would also require a lot of work in training the real estate agents on how to understand the things that make no sense in their region. Accuracy and consistency would surely go out the window. The person in charge of quality control might even be in India if the MLS went national! The whole idea makes visions of nightmares float through my head!