Location of People in Twitter (iPhone)

Recently, I was working on the data of the twitter. I did one interesting and quite simple thing. I took the list of the location people were using in there profile and fed it to one of the available online tool called (http://www.wordle.net/). Guess what I got? I found that majority of people on twitter seem to be using iPhone. May be it was obvious, but to see it through data was quite a taste. The size of the population used is 31691.