Vicyankees posted a WebmasterWorld thread that explains that when searching with a site command at Google, using site:www.domain.com, Google now returns results that may be sub domains.
For example, when I conduct a site search for site:www.seroundtable.com I see in the second result, the listing, "forums.seroundtable.com." I have never seen Google return a forums.seroundtable.com result before, when using a site command. Yes, I use this site command search very often.
Excluding the site command by sub domain does work, so a site command on site:forums.seroundtable.com only returns results from forums.seroundtable.com. That is good, but I will really miss being able to exclude the site command by www only, since I constantly search for articles only on the www.
To be clear, a site command for site:domain.com always brought up sub domains. But I specifically used site:www.domain.com to bring up only results on the main directory. If you have a site that redirects www to non www, or only do site commands with site:domain.com (i.e. without the www) you would not notice much of a difference here). But I find the site:www.domain.com search very valuable.
If you don't see this happening, try these IPs, 184.108.40.206 or 220.127.116.11 or 18.104.22.168 , or 22.214.171.124.
More importantly, does this mean that Google sees subdomains as part of the main domain? In the past, subdomains were seen as standalone sites, for the most part. Now, is that still true?
Forum discussion at WebmasterWorld.
Update: Google has informed me that this site command change was not an intentional change and we should expect the old behavior to return relatively shortly.
Update 1/29/07: I still see subdomains returns for www site commands. I am not sure why it has not been fixed yet.