Re: So much wrong with this.
I use DHCP on my local network with static allocation of IP addresses to known MAC addresses.By the time you add in phones, PCs, game consoles, laptops, printers, virtual machines (doesn't everyone have one?) etc, it's very quick and easy to have twenty or thirty devices on a network.
I used a couple of Sheevaplugs as DHCP/DNS servers in a master/slave arrangement. Setting it up taught me how it works, and when one of them died for some reason, the other kept things going while I fixed the broken one.