I put up an entry on a Singaporean youth being caught for "stealing" his neighbour wi-fi connection previously.
Now in UK, similar cases were reported but in these cases the offenders were just being cautioned for using the wireless connection without permission or to be precise being dishonestly obtaining electronic communications services with intent to avoid payment.
Read here and here for the complete story.
Again, the issue that would like to highlight here is who's responsibility to secure the home WIFI systems? Is it Owner or Service Provider? In this case, the police advised people with wi-fi should follow security advice given by their internet provider.