Yeah, I think a whole country is extreme, but as a forum admin I've seen spammers that change IP addresses with every spam but the addresses are all within a subnet, so I would just block the subnet. In theory that may block a few valid users, but the payoff was that it sometimes kept spammers from polluting and ruining the forum for current members, and it didn't block every single address in the originating IP block. For me and the forum the benefits outweighed the losses.
And then there's the spammers that spoof IP addresses and switch subnets and IP blocks. That's tons of fun.