A WebmasterWorld thread uncovers a very interesting occurrence that is taking place when using a site command feature, known as the "hidden" or "invisible" site command search.
If you want to search with a site command but don't want the referral data to show that you are using a site command while searching, you use to be able to use a flavor of a Google Custom Search Engine to get at it. The example given is:
Notice that when you search using that command, up come videos from YouTube.com or video.google.com, included in the webmasterworld.com results. A site command is suppose to restrict the results, only to results from that site, i.e. webmasterworld.com.
At first, I thought it may be an issue with Google Custom Search Engines. Because last night, TechCrunch reported that there was a major outage with the Google CSE. But Google said they fixed that, so that is not the issue.
Maybe the thread creator is right:
I suspect google have deliberately broken this method of site searching precisely because it is invisible to the user, and they would rather people use the Custom Search Engine system instead. But that's just the cynic in me.
Who knows, maybe this is the wrong query string in the first place?
Forum discussion at WebmasterWorld.