Their methodology, from their site:
This list was compiled by searching Google’s top 100 results using terms like “real estate blog” and “property news”. In this respect it is biased towards English-language sites. We also searched the blog rolls of some of the biggest blogs in the UK, US and to a lesser extent the rest of the world to add to the list. It took us several weeks to compile a list of over two hundreds sites. We then used the SEOMoz Trifecta tool to rank the importance and notoriety of the sites most relevant web page (we link to the page we ranked).
As a result, the list is a curious mishmash of news sources, portals, blogs and other web-based sources but interesting nonetheless. I picked up a number of new sites I’d never seen before.