Except in rare cases Trulia does not receive listing information from the MLS. Listings are submitted to us by brokerages, brokers, agents and web vendors.
From what I've seen properties listed on our site as active that are really sold come from web vendors. Generally it seems like agents create single property sites or listing virtual tours but forget to update them once the property has sold.
Please note however that you can easily report these errors to us using the red flag you see on the listing detail page and we're always working to improve our filters that allow listings onto our site.
Customer Service Representative
Thomas that, at least for the time being, you can be sure that you are fully aware of everything for sale by working with an agent. Many will be happy to send you MLS listings that fit your criteria without trying to hard sell you on their services. Good luck.