Here is an interesting article on how Wikipedia blocked the whole nation of Qatar because someone spammed. Apparently the whole country is NAT’ed – appearing to the whole world as having one IP address.

…that resulted in the accidental blocking of the entire nation because Qatar’s sole telecom, Q-Tel, funnels all Internet traffic through that single address, a practice that allows the country to monitor and censor its users, said David Gerard, Wikipedia’s London-based spokesman…

Here is a try IP space conservation! It makes it easy to sensor content as well!