Finding and analysing suspected duplicate registrations - a challenge!

[Spinball]

Hi folks,
I find that sometimes when we have to ban an idiot from our forums, they quite predictably re-register and continue to plague us.
May I request a hack which helps admin to find people with duplicate IPs and analyse their posting habits to see for sure whether they are the same person?

The hack would be in two parts. The first part would find people who are banned by moderators, and for each one, sift though the database to find other users with the same IP (in posts and registration).

A list would then be presented of each banned user and the other users having shared IPs. There is a 'Go' button for each banned user. Each IP sharing user has a tickbox next to it. Admin picks the banned user they are interested in and selects at least 1 of the IP sharing users for that banned user.
Admin then clicks the 'Go' button for that banned user and a report will show the threads & posts of the banned user and the selected IP sharing users.

I have previously used the following SQL statement for the purpose of the report:

SELECT forum.title AS forum, thread.title, FROM_UNIXTIME( post.dateline ) AS date, username AS user, concat( 'http://www.yourdomain.com/forums/showthread.php?threadid=', thread.threadid ) , post.postid, post.ipaddress
FROM forum, post, thread
WHERE post.threadid = thread.threadid
AND thread.forumid = forum.forumid
AND (
username = 'suspect1'
OR username = 'suspect2'
)
AND post.threadid = thread.threadid
ORDER BY post.postid
LIMIT 10000

Where suspect1 and suspect2 are the user names of the suspected duplicate registrations. Obviously they could be user ids.
The report shows what each user posted and when. By looking at the date and times and IP addresses, it's possible to easily identify posting patterns which are very strong evidence of duplicate registrations.

For people with busy boards and a lot of banned users/spammers, it would be very useful to be able to track down trouble making re-registering people and have some stronger evidence of their multiple registrations.

There's a challenge for some whiz coder!
Cheers