sensor (required) — Indicates whether or not the geocoding request comes from a device with a location sensor. This value must be either true or false.
requests without it are denied:
“REQUEST_DENIED” indicates that your request was denied, generally because of lack of a sensor parameter.
Why is this? Why do they want to know so badly whether the request comes from a client with a sensor or not?
Is it for statistical reasons, or to be able to provide services in the future?
The sensor parameter is required by Google as they need this information for statistics as part of their licensing terms with their data providers.
Taken from this Google Groups post (from a Google employee by the looks of it)
The sensor parameter doesn’t give you
any geo location capabilities it just
lets us know as part of our licensing
terms with our data providers that the
map is being used in conjunction with
some sort of geo location