Law Enforcement is unlikely to chase either. The MPAA could spend vast amounts of money to chase the first and gather evidence which LE may then later use(as the RIAA is for illegal music sharing). So far they have not done so. But mostly the cases you hear about are Civil not Criminal. AFIAK only one person has been prosecuted here in the states so far for hi-jacking wi-fi. And he was in his car in front of the person's house downloading child-pornography on his laptop. The owner of the AP saw him, called police and he was arrested. Hijacking wi-fi is the least of his legal (or psychological) problems.

Not to mention that the first scenario you mention is a federal crime. The second is a local one and police response will vary greatly from jurisdiction to jurisdiction. There are cities where even if your car is stolen, they won't send an officer to you. You'll have to go to the police station to file a report. (Which can be difficult without a car...) Is this because the police don't care? NO. It is simply Triage. In higher crime areas, violent crimes receive more attention than non-violent, major crimes more attention than minor ones...

An IP address is just a number. Proving that you received a phone call from a particular number is not the same as proving you received it from a particular person. But a picture is worth a thousand words. It is something any cop or prosecutor can wrap their brains around and doesn't take an expert witness to explain to a jury. This increases the chance of a conviction and reduces the cost of a trial...

cheers,
kernelpanic

p.s. -geminiii42, aGPS is supposedly coming with Diablo and works well. I'm trying to get a working framework up in time for that...