I just read this article about MLSs, Property Portals and Real Estate Agents spending many millions of dollars on anti-bot software.
Just to lay this out clearly: companies that put data onto the internet want to choose who can take that data and what they do with it.
The best line in this article is the head of an MLS comparing her listings data being scraped to jewellery being stolen from a store.
This all goes back to who owns the data. Is it the MLS, the brokerage, the agent (who does the listing work) or the property owner themselves? It's entirely ambiguous.
Ultimately, this listings data exists to serve a single purpose: to advertise a property for sale or rent in the hope of attracting a buyer/renter enquiry.
If a bot scrapes that data, what does an MLS or Real Estate Agent lose? Absolutely nothing. They still make the MLS dues and sale commission they would have.
What does anybody stand to gain from scraping data they cannot immediately monetise? Answers on a tweet.
Here's the article on anti-bot software: http://www.inman.com/2013/08/01/coordinated-effort-to-target-real-estate-scrapers-launched/