May I suggest that the board limits to registration per IP address as a new feature.. like allowing only one email address to be used once?

weird suggestion..

do you want it to be possible to use an emailaddress once for registration? or do you want it to be possible to limit the number of registrations coming from a specific emailaddress?

I'm pretty sure he justs wants an IP to be able to register on his board just once.

Wouldn't be very smart, as this causes SEVERAL PROBLEMS.

For example people who use proxy servers, people who use Google Web Accelerator, people who go to Universities, are just a few examples...

In addition, in some rare cases - different users are assigned the same IP address by their ISP, and that blocks access

I like the intent of this suggestion. Rather than limiting multiple-registration, there could be an option requiring such registrations to await manual validation by an Admin.

For our board, I would simply like the ability to get a list of all IPs that have been used by more than one user: across registrations, posts and poll-votes.

A related idea would be to have an IP warn list, similar to the IP ban list. Anyone registering via one of those IP patterns would require manual validation by an Admin.

I support this!