Yesterday I experienced an utterly depressing visit by an engineer from a certain major (OK, biggest) ISP. The home gateway wasn't working and he replaced it, but then came the network password issue.
The key on the CPE worked fine for my Linux netbook and an iPhone, but not a Windows 7 laptop. So he said he would change it, and suggested, nay insisted upon... 0123456789. We protested. No, he said, people wouldn't guess it (I'm not making this up, by the way). We refused.
Cue much palaver testing various keys on various devices, but eventually we found something that would work on everything: a WEP key with few letters mixed in. Great. Now, on the issue of the 0-9, this engineer told us many Windows Vista/7 PCs have Wi-Fi password issues, and the ISP's standard Huawei home gateway is partly to blame, and he therefore usually sets customers' security to 0123456789.
Hence the depression. In the context of the Digital Economy Act, if this is the norm, we can look forward to an awful lot of court cases.