Edina Realty, one of the largest brokerages and a dominant forces in the state of Minnesota has decided not to feed its listings to Realtor.com and Trulia. It is common to hear grumblings from agents and other industry insiders that giving public sites access to their listing data is in the end counter productive and leads to deterioration of one of their prized possessions, MLS data. It is hard for me to see the benefit to the clients of their company.
I think that it is unlikely that you will see many others follow suit. Competitors of Edina Realty are likely to use this as a selling point to gain market share.