IP-based restrictions should not be enforced in any way. Most ISPs outside of the US give the same IP address to hundreds or thousands of end-users in different premises, in much the same way as anyone playing at work in a large corporate network will have the same address as his fellow co-workers.
D.
I agree with this. You use some type of cookie or even a MAC address to limit the connection to 1 per computer, but I like the ability to play with people in the same household or workplace. We the rankings moved to an ELO type ranking system like I recommended here:
http://www.planetmule.com/forum?topic=554.msg2591#newthis wouldn't make as big of deal in the rankings.
I think people are going to be able to manipulate almost any ranking system and there should be way in which this is controlled as best possible, but this is not the answer IMHO.