When you create a new file in Xcode, it creates a comments header with the project name, your name, and your company name:
// MainViewController.m // TestProject // // Created by J. Kira Hamilton on 10/19/11. // Copyright 2011 _MyCompanyName_. All rights reserved.
If your company name isn't set, then it defaults to _MyCompanyName_. In earlier versions of Xcode, you could use a "defaults write" trick in the Terminal to set this value, but Xcode4 changed this. Now all you have to do is set your name and company info in the Address Book app.
You can also specify the company name in Xcode (for this specific project). Click on the project name in the navigator, then go to the Utilities frame on the right side of the Xcode window. Set the "Organization" value there.