My IP address at work, on my DSL or cable modem line, and through each of my dial-up ISP's (I can use Compuserve or Earthlink) is different. (actually, they are all DHCP, so they won't be exactly the same even from time-to-time).

Someone with the resources of the NSA or CIA could no doubt trace all of this and find a person. But it is a bit much to ask of the Flyertalk staff.