The talk about "hyper local" and relate it to the 5 digit zip which can still encompass thousands of people. Hyper local to me would be if the went to the 9 digit zip, which would be basically a city block, or apartment building/complex. Of course if they went to the 11 digit number in the postnet bar code (9 digit zip + 2 digit delivery point) that might be going too far, essentially each individual house or apartment.
With all the location data on tweets now, how long will it be until this is really useful and twitter allows you to just follow a radius of a given lat/long?