Hi Mark. The technique is commonly called "geo ip" targeting. The concept is that a computer's geographical location can be determined by the IP address/block initiating the request.

Can't say that I've never done it, but don't care for it. People feel spied upon enough, and when they see ads targeted right to their hometown it will spook a lot of them right off the site. Nothing wrong with it, but even a warm welcome thanking them from visiting you from Wherever, USA might fall create a feeling of "You have more information than I am comfortable with."

Most IP targeted content is served up in a way that is subtle, and that is the smart play at this time, IMO.

People have no idea how much you can learn from just a single visit - and wouldn't like it. I have no problem with it, but the average person I think is not ready.

Seen that on dating ads. Of course with the way dynamic IPs are allocated in the UK the town name quoted is never anywhere near where I live and is different nearly every time I see one.