In the past years, SEOs have known not to use the site command or operator, i.e. site:www.domain.com in Google to determine the number of pages indexed for their site. Instead, they relied more on the Google Webmaster Tools area, in the Sitemaps section, that shows how many pages were indexed versus how many pages were submitted in the XML feed.
Although the Sitemap method is not 100% accurate in showing how many pages are indexed by Google, it does show you of the pages you submitted in your Sitemap file, how many of those are indexed. A site command was suppose to show you the pages Google indexed in the sitemap file plus other pages you didn't submit via a Sitemap file.
The thing is, the site command hasn't been useful to many.
A WebmasterWorldthread is discussing the site command and what appears to be recent changes to it. People are now thinking it is more accurate, less buggy, then it was in the past.
Forum administrator, Tedster, said:
This sounds like Google has repaired some of the inaccuracies that the site: operator has been showing for a while. In other words, the index does not really include more pages but the site: operator results are not quite so buggy.
I just spot checked a few website, and it does look like they're back to reasonably accurate levels again.
Personally, this site shows of the 10,000 URLs submitted via a Sitemap XML file, 9,419 URLs in web index. But the site command shows well over 15,000 indexed URLs on the main www version of this site. It does seem somewhat accurate to me.
Forum discussion at WebmasterWorld.