Ah, that is a horrible analysis. They are wanting to estimate the number of people with these skills by searching on hashtags, but they search only on the term "objective-c" when what they really should be searching on is Cocoa, iPhone, iPad, iOS and other terms that require one to be working in Objective-C. There's not so much to Objective-C itself that there's a lot of discussion about the language itself compared to what it is used in.

Also, in general I don't buy into these methodologies where someone spends a few hours doing searches on internet boards for certain keywords as a way to estimate the number of people with various skills. It's not been shown to be a valid way of getting accurate data.