Search Engine Roundtable published an article this week with some information they received from Matt Cutts of Google regarding the way subdomains will be treated in Google’s search engine results pages (SERPS). This is what Matt announced at PubCon:
Google will very soon begin treating subdomains and subdirectories the same in this fashion: there will be only 2 total urls from a domain in any set of search results, so no more getting 3, 4 or however many spots via subdomains. We didn’t get any more information than just that basic heads-up.
Currently sub-domains are treated as a separate entity, allowing for websites to have multiple results show up. For example here is a screen capture of a navigational search for the query “Search Engine Roundtable“…

How Will This Affect Business?
Search Engine Land has some interesting insight into the implications of a change like this. In the following example the top 3 results for a search on “macbook” are displayed.

You will notice the 4th result is from the store.apple.com subdomain. Losing these types of subdomain results could cause significant traffic loss and a noticeable decline in profits for some big business.
How Will This Affect Users?
Some say this will allow for more diversity and better search results on the whole. There are some interesting comments from both sides of the fence on this issue at this Sphinn page. In light of all this, the Google bots are doing some good things such as the recent increase in possible “Sitelinks” for popular websites.