First, excuse me for my English.

There are lot of requests on ban of whole countries at the forum, but i wish to propose slightly different direction.
My situation: DSL provider gets speed of 64k (download) from any ip's excepting ip's of this provider - they can download each from other with max of 150-200 kbytes/s (and sometimes more). Provider doesn't use subnetwork at all, all users have addresses from three ranges (saying 78.*, 91.*, 90.*). I want that Ktorrent prefer addresses from pointed ranges, and after announcing kick other peers in flavour of provider's ips. This can also useful for those who downloads torrent outside one's local network in company with other people from the same network.
(Currently i manually kick low-speed peers - i don't know exact addresses of people who download eg popular torrent simultaneously with me)

I think this would give KTorrent an extra over other clients.

OK, why not, we will add it in 3.2

Sounds really like we want to compare the number of hops between us and other peers and give preference to those with lower hops.

In fact, that's part of the P4P proposal, and really makes sense, selfishly speaking, regardless of what the ISPs think. It would lower the actual internet usage since more of the traffic will come from inside one's own ISP, but for us it means faster downloads.

Yes, it can be solution too

Azureus has similiar feature. It is called Local network or local peers (don't remeber exeact name). It allows to specify subnets which are treated specificaly then others