Hi again!
Another challenge I have is on one site, users keep signing up multiple times with more than one account. That's a problem, as multiple accounts is against our site's TOS since we frequently have votes that are one-vote-per-account. Our legacy system that we killed when we moved to Drupal had built-in IP logging every time a user logged in, so we could go in and check IP addresses in case we suspected a duplicate user. We could also see the IP address someone signed up from, and match that against any recently logged IPs.
Does anyone know of a similar tool for Drupal, or is this another module I'm going to have to write myself? :-)