It's a nightmare. I used to work for one of the industry dinosaurs; they have an MLS team that was as large as their development team. They pull data from over

It's a nightmare. I used to work for one of the industry dinosaurs; they have an MLS team that was as large as their development team. They pull data from over 600 MLSes, with different requirements for each. Managing 600 business contacts is a big pain, then there are different data conventions that change without notice. They have had a long-standing arrangement to feed data to Trulia too. The word is most MLSes use CDNs, so scraping might not be the best way.