I think with the rise of companies like Skyhook, it's often untrue that IP address "is a very rough and unreliable indicator of location". There are people very actively trying to correlate IP addresses with ESSIDs and GPS observations; inaccuracies in their databases will mostly come from ISPs reassigning the IP address, which may be a rather rare event on some large networks.
We could have an informal experiment with an "Ask HN": go to Google Maps in private browsing mode; can you see the building you're in or the street you're on within the mapped region?