On most sites, if you try to submit an empty form/query, Javascript alert box will be thrown right in your face, but not Google. What do they do with number-of-times-nothing-entered-search? We are "told" to conserve precious network resource :p

If you are saying that the blank searches waste network bandwidth, I would argue that adding the extra JavaScript to every page would waste more than the blank searches

I was going to say exactly what Stephen said: If the number of blank searches produces A wasted bytes, and the weight of the script to check if the search field is in blank is B bytes, then:
A must be bigger than B * number of pageviews Google has during the same period of time we are messuring A.
Indeed, probably they are saving precious network resources right now :)

Very good point indeed. But I think there is more to it than just that. Especially from a company which even captures your mouse-over events of Google Ads. Google is information hungry. I was wondering if anybody would come up with a possible use of capturing such data.

Ram, NOBODY use JavaScript validation in such cases. Validation makes sense when form's point is to add data to the database, and it is important that this date wouldn't be corrupted. For example when adding a comment or registering a new user. There would be no point in using this technique in websearch, and this would be extremely annoying.