You have to be careful. Using it once i think is ok but everyday is not...
Regarding the police when they will come out but it all depends on where you live! I was in the process of moving from a very expensive area and was living in a crap area.... I called the police and they never arrived (just a letter). I moved back to an nice area and called the police and they turned in in minutes.
If you have logging enabled on the router it nice and easy to obtain a MAC which cannot be changed and is unique - Yes you can use MAC spoofing but then again why would you be doing this. The law is getting very strict on this as people are logging and to open wifi and accessing child porn - even with most ISP's using the IWF proxy servers.
The chance is very small of getting done for doing it though i would not as you can get done... Just go to wetherspoons and buy a pint to get 30min free wifi access!
