I read on an agent's blog that enhancing listings on Realtor.com allowed them to put a link to their website on the listing which they believed would help with their SEO. Unfortunately, this is incorrect.
What Realtor.com, Trulia, and other listing sites do is put a "nofollow" attribute on the outbound links. According to Google "when Google sees the attribute (rel="nofollow") on hyperlinks, those links won't get any credit when we rank websites in our search results."
If you want to verify, just go to a listing page and choose to "view source". Then under the Edit menu, choose "find" and put in "nofollow". Or, just search on your website url and look at the entire string to see if it has ref="nofollow" in it.
Keith Byrd
www.SloCountyHomes.com
San Luis Obispo, CA