It’s useful to change /etc/hosts, especially with protections requesting online keys. After editing /etc/hosts you need to refresh OS X NetInfo Database. Just run the following command:
$ sudo niload -v -m hosts . < /etc/hosts
And then flush cache with:
$ lookupd -flushcache
For Snow Leopard the command has changed. It is now:
$ dscacheutil -flushcache
And that’s it!