[Google Maps API v2] "request denied" on example

I was browsing this page: http://code.google.com/apis/maps/documentation/elevation/

and I tried pulling the example with PHP using file()

http://maps.googleapis.com/maps/api/elevation/json?locations=39.7391536,-104.9847034&sensor=true_or_false

and got this result:
Array(
[0] => {
[1] => "status": "REQUEST_DENIED",
[2] => "results": [ ]
[3] => }
)

Why?

--
You received this message because you are subscribed to the Google Groups "Google Maps API V2" group.
To post to this group, send email to google-maps-api@googlegroups.com.
To unsubscribe from this group, send email to google-maps-api+unsubscribe@googlegroups.com.
For more options, visit this group at http://groups.google.com/group/google-maps-api?hl=en.