Pooliekev wrote:
Send him a load of kiddie porn and ring the filth??

More likely you'd get the visit.... it has actually happened at least once where some unsuspected person with an open wireless connection has had a visit from the boys in blue to discuss their browsing habits... and has only then realised that a neighbour has been taking advantage of the connection.
There was even a trend for a while in London for people to make chalk marks on buildings where they had found an unsecure wireless network as a sign for others... once they realised what was going on some of the IT people kept a lookout for them as they then knew they needed to toughen up the security.....
Either WEP or WPA protection, one is more secure than the other but either is a lot better than nothing.