Why is realtor.com showing so many duplicates?

http://www.realtor.com/realestateandhomes-search/12015/type-single-family-home/type-land?ofbm=100

First pages is pretty much taken up by 2 homes for sale, displayed over and over.

In my area, at least, some real estate firms are in more than one MLS. If both MLS are on realtor.com, that results in a duplication. Even though I sometimes use realtor.com to search for listings outside my MLS area, I find it slow and cumbersome. I think there's plenty of room for improvement.