To his list of reasons, I would add compatibility and ease-of-use. The number of devices on my home network is now over 20, most of which are wireless. Most don't support the "really secure" new protocols like WPA, and configuring them to work with security is usually either annoying or futile.
I've debated just having two networks, one secure and the other open. The article points to Fon having WAPs which do both. That's better than buying multiple WAPs, especially since I already have two in my house to get full coverage.
Update: Ok, most of the devices probably do support WPA, though even one that doesn't is enough to be annoying.