(No more Olmert! No more Kadima! No more Oslo! )
As ridiculous as these charges were, I'll answer your actual question, at least partially:
Since people started garbage raiding for identity theft;
Since PIs & "Activists" went on garbage raids, to dig dirt on people;
Since some idjits raided store dumpsters, then sued when they got sick on tainted luchmeats, deli items, etc that the stores had discarded;
People suing the store, when they get hurt while trespassing to dumpster dive;
Since the ACLU was able to win some cases involving cops retrieving incriminating evidence from trash cans without a warrant.
I'm sure there are more reasons, but that said, I still do not agree with the severity charges nor penalties in this case.
Something about penalties fitting the crime, etc.
As a one time dumpster diver I have to say this is sick. I know that in America, they have anti-diving laws because if someone ate the food and got sick, they could sue the store. But, c'mon its GARBAGE. How many people have "dived" furniture that someone was throwing away? I wouldn't have had a living room in college.