We currently us a third party system to resolve user's IP addresses to domain name. It helps our advertisers better understand the type of exposure we're providing them. I thought to myself
Surely, Google Analytics can be configured to do this for us or there must be a 3rd party tool that we could bolt-on.
Well, the answer, apparently, is no to both. It turns out that Google views the user's IP address as "private" (for reasons I can't understand seeing as it is transported on the public internet with every request!) and so doesn't make it visible through Analytics. They do, of course, capture the user's IP address as this is how they do the geographic reporting.
Also, there were some hacks around at one point using filters to scoop this out, but Google has shut those off as well and reminded us all that the Google Terms of Service prevent this anyway.
If anyone out there has solutions for doing this, I'm all ears!
In the mean time, this article had an excellent summary.