Security issue.
Y'see, I don't want to share my internet connection out with the entire neighborhood - and as we're all aware, the current protocols for wireless security are pretty much a joke. What I was going to do was to run a two-way firewall, and only allow VPN'ed traffic through in both directions. Anything that couldn't connect to the VPN would find itself in a dead-end situation, a network to (literally) nowhere.
They say a city in the desert lies/ The vanity of an ancient king/ But the city lies in broken pieces/ Where the wind howls and the vultures sing/ These are the works of man/ This is the sum of our ambition...