There should be a way to do a search on IP addresses in RC.
Ex.
/findip #.#.#.#
would give a list of accounts with that IP address as the last IP.
/findip #.#.#.*
would give a list of accounts with that IP range matching the last IP.
and so on.
This would probably be useful in recognizing possible account theft and possible impersonation, as well as a quick way to tell if a single IP is spamming your server with several trial accounts online at once.