Violating their privacy? That's kinda strong language for reading somebody's IP address off of an HTTP request, don't you think? Any time I visit merlyn's home page, I get that information thrown back at me, and don't think twice about it.

The perception of violated privacy might get a few people antsy, I suppose, but only if you're rubbing their noses in it. I'd be much more worried about the technical aspects of it, and it sounds like an acceptable solution exists (provided it's not mission-critical. I can't imagine how it possibly could be mission critical, of course, but somebody had to say it...).