la la la la la - I'm in bradford - this cunning site shows me as being in Manchester (at the moment) (30 is miles out)
that's on a bt dynamic feed
with fixed IP of course
http://www.demon.net/external/
will pin you down to the address of the registered owner
you are almost certainly running a dhcp server - so the ip address of the company (wan) - and yours (lan) will be different
but your mac address - which has to be included in the packets - Identifies your machine
so I could probably meet you in the carpark tonight if I had your IP address and was pressed.
however - mac addresses aren't registered to users - so the ip address links to customer - and then an internal search finds the actual machine.
generally this last step would only be available to the police (or security services) - as would the internet records (kept 3 years) held by your ISP
to put it into perspective
about 6 months ago a letter arrived demanding either �600 by the end of the month - or a day in court at a friend's house
The letter included the ip address (which had changed by then) and the mac address (which matched)
He rang me for advice - suspecting a scam
the solicitors is a huge firm in the city - (he works just round the corner) he visited the firm - was assured that it was kosher - and payed his �600
later in one of the local papers he saw that prosecutions were ongoing and (fines were in the area of �12000).