If I was an interviewer and a job applicant told me that he would "google" the answer to a question, I would quickly show him the door and put his resume in the circular file.
http://www.infoplease.com/askeds/number-gas-stations-us-1995...
If you want the candidate to show his reasoning abilities by making good guesses based on reasonable assumptions, you should tell him to do so beforehand.
I'm a hardware engineer. As shocking as this may be to some, much of what I need to know cannot be easily found on the internet. I have to crack open a book to find good high level information. With the rising popularity of open college classes, this will probably change, but we aren't there yet.
For programming, the internet can be a very good resource. When I was a full-time programmer, google served as a very good reference. I would open a browser before I took a look at my bookshelf.
I want practical, get the job done type people.
I don't want cowboys who are more interested in clever solutions and/or impressing others with their knowledge, "obvious" intelligence, or skillz.
I certainly don't want some douche sitting in his chair theorizing from first principals when they could have googled the answer or asked team mate for help.
Finally the era when what one knows was self-contained in their heads is over. My memory and knowledge are huge and they are kept in google and wikipedia.
It shows that someone is willing to go and seek out the answer on their own.