I was at the local Apple store to have them replace my iPad, which had a defective home button. I asked the Genius Bar rep about the rattle, and he said they know this is an issue. Interestingly, he said that this is "hit or miss". In fact, he said they had phones that have the rattle and those that don't. Either way, Apple doesn't replace a phone for this, so it's really a moot point.