Hi Jack, I'm a Bay East Assoc of Realtors MLS Council member and I think I can provide some clarity here.
When an Association of Realtors is formed in a defined geographic area a MLS database platform must be decided upon (there are a few handfuls of standard software providers for this). After establishing a MLS system various AORs may decide to share information between them. There are standard data exchange protocols for this. If you are working with a Realtor its very important to know what geographic MLSs they have full access to.
Trulia and other "3rd party listing services" you have mentioned are not AORs; however, these service providers negotiate "data feed" agreements. Some AORs agree to these, others do not, and this is where comprehensiveness suffers. In cases where an AOR does not agree to a data feed agents can still upload listings manually. If not managed diligently old listings can remain on these sites. Trulia has negotiated direct-feed agreements with many AOR MLS systems, but it will be some time before its comprehensive.
One of the other issues with "3rd party listing services" is data integrity. I canâ€™t even count the number of times I have had to inform home seekers about RealtyTracâ€™s deceptive data feed on Trulia (donâ€™t get me wrong, I like Trulia, but I do not have any love for RealtyTrac). RealtyTrac is not a MLS; they just take public record and tease you with it so you will pay them a monthly fee to get more information. Most foreclosures are listed on the Realtor MLS sites - at market value, not the low price shown by RealtyTrac, which is nothing more than the amount(s) in default. . So, I enthusiastically submit the following to you: To remove all RealtyTrac â€œforeclosureâ€ listings from your Trulia search results go to your search results page. Check out the Refine Search box on the left and scroll down to 'Listing Type'. Uncheck the 'foreclosure' selection and your search will update automatically and filter out all RealtyTrac listings.
As far as obtaining the most up-to-date comprehensive information the â€œMasterâ€ you should be using is Realtor.com because it pulls its data directly from all AOR databases nationwide. Once a property goes Pending or Sold it does not show on Realtor.com; however, other sites not directly tied into the AOR databases will show properties as Active when they are sold. While Realtor.com may be comprehensive, it can still be a little â€œclunkyâ€ from a User perspective.
Currently, there is an ongoing effort to establish a CA Statewide MLS, but it looks to be 12-18 mos. away; however, I'm looking forward to this being established.
In a nutshell, your best source for up-to-the-minute information is a local Realtor. I would suggest that you team with a Realtor and have them set up an automated "search agent" for you so you get notifications (that match your search criteria) automatically via email as soon as they are made on the MLS.