Many (most?) web server configurations require a 'Host' header specifying the domain to be accessed (which allows multiple domains to be hosted on a single IP).

Many (most?) web server configurations require a 'Host' header specifying the domain to be accessed (which allows multiple domains to be hosted on a single IP). So in a lot of cases just typing the IP into your browser won't be enough, but thats pretty easy to work around. The greater difficulty is ascertaining where a domain should point to once it has been seized. One solution is to grab the old records from a DNS cache, but then there is no way to update them should the IP ever change.