I just tried it with my Flickr key and it works. I called it like so:
NSLog(@"%@", [FlickrFetcher topPlaces]);
By the way, you are doing the Fall 2011 version of the course which is iOS 5 based. There is a new Winter 2013 version of the course which is iOS 6 based which can be found here:
https://itunes.apple.com/us/course/coding-together-developing/id593208016