And yes, if someone did commit a crime using my network the police might visit, but what better defense is there than the fact that I have an open wireless network? If I enabled wireless security on my network and someone hacked it, I would have a far harder time proving my innocence.
In Germany this defense wouldn't really help you much. You're (partially) responsible for the crimes that are committed over your unsecured network. It's called "Mitstörerhaftung".
Where does he live? It makes a huge difference if he lives in a farm house in the middle of a field or if he lives in an apartment building in the middle of a a large city. If you live in such a way that the only way for me to see your network is to sit in my car in your driveway, then perhaps. However, from the comfort of my sofa in my living room i can 'see' at about a dozen different wifi networks (and by extension at least a dozen people can see my wifi network from their sofa).
That kind of changes the math a bit. I don't want a dozen people torrenting off my network, not because I'm afraid of getting in trouble, but because it degrades my ability to use my network.
I've had enough experience with being cut off first and asked questions second. Running a server at home, this wasn't pleasant. I don't fancy trying out how often random people manage to cause abuse reports with my ISP - let alone the police. Besides, wireless isn't magically limited to the confounds of my home and garden. It's not basic politeness like a cup of tea as the page claims.
How often does this actually happen? I am just not worried about it. I have been running open wireless access points at every home I've lived in for the past fourteen years.