On my wifi network there are two Mac (MacBook,MacBook Pro) and two iPhones (iPhone4, iPhone 5).
The MacBook Pro has been updated to OS X 10.10 Yosemite. The MacBook cannot be updated to OS X 10.10 Yosemite.
Location Services work fine on the phones (but they have GPS in any case).
On iCloud.com "Find my iPhone" finds all the devices, and gets a location for the iPhones and MacBook, but not the MacBook Pro. "Find my iPhone" can send an alert sound to the MacBook Pro and that works.
Also on the MacBook Pro the location is not found for the Weather or for Maps or for Google Maps in Safari.
Seems to me Location Services are not working for the MacBook Pro.
I have tried turning "Find my Mac" on and off with no result.