Cannot query SP.UserProfiles.PeopleManager from the App Web via REST

I'm testing REST results in the browser with mixed results.

The following URL returns the expected result:

http://ift.tt/1E7rCte

however the following URL returns an error:

http://ift.tt/1IB3K00

I get the error code -1, Microsoft.SharePoint.Client.ResourceNotFoundException and error message Cannot find resource for the request sp.userprofiles.peoplemanager. Google doesn't offer up much for the errors. Fiddler responds with a 404 result. I've tried leaving the URL unencoded, tried with lower case sp.userprofiles.peoplemanager and getuserprofilepropertyfor with no luck whatsover. I have also tried other methods within sp.userprofiles.peoplemanager. What am I doing wrong?