The intellectual property history behind iPhone is quite interesting - the Wikipedia article about iPhone trademarks and IP issues is worth a read.
In terms of real-world impact, we developed unlockediphones.net as an iPhone news & market aggregation site for the last several months. Initially, our effort was on designing the site and working on SEO issues. Once the content system was finalised and we started ramping up traffic to the site (grown from about 20-30 visitors per day in 1st 3 months of 2009 to 150-200 per day in April/May) we focused on doing some monetization to recoup our dev efforts.
All that to say that at no point was there any C&D or legal interaction with Apple. Of course, there shouldn't be - we are providing a venue that furthers the interest in their product. If you are considering using the term iPhone or iPhones in "bad faith"... making a site that could be "confusingly similar"... or "diluting" the value of the iPhone trademark, then you could be looking at a darker set of circumstances.