Honestly I can understand zillow's side here but I'm just curious. Shouldn't the original use of izillow.com been grounds for trademark enforcement? The only thing I think is less than savory is that now, when you have your own iPhone application, you're going after this person and making sure people don't mistake it for an official version.

But like you say, there are details here that have not been disclosed, so I am by no means passing any kind of judgement.