Did you specifically ask the originator of the popcorn before you grabbed a handful while the bag was being passed? They might not have intended for YOU to actually have had any, only the others around you.
On topic again, the issue is one of severity and actual damages.
I don't dispute that copyright "theft" should be illegal and have SOME kind of punishment. However, when it comes down to it, a lot of enforcement out of necessity should be the province of the copyright holder. I think the government needs a role as well, but it shouldn't be the role of monitoring. In general police don't actively monitor your store or your house or your car to make sure nothing gets stolen. It is your job as the property owner to monitor your own property and alert the government (police) if you suspect a theft or break-in. THEN it is the job of the police to investigate based on the severity and scope of the crime.
In the case of a technological copyright theft, it isn't simply a case of a right's holder telling the government, "Some people have stolen my IP, go stop them!" I think it requires and honest to goodness, "Here are the particulars as far as I know them, can you please investigate further".
These days copyright theft over the internet is a lot like blood typing to identify a criminal. You might be able to narrow "who dunnit" down to a specific IP address. Supposing the IP address wasn't spoofed then you can track it down to an internet account holder. That doesn't mean that internet account holder actually did it, only that it came over their connection.
If someone used my car to rob a bank that doesn't mean I should be held liable. Sure, I should be at least looked at with a bit of scrutiny. After all, I would hopefully have some idea who used my car. However, if my car was stolen, I am probably not going to have any idea. If it wasn't stolen, hopefully I have a darned good idea who did it. But, if I gave 10 friends and all of my family members the keys to my car and I rarely look in my garage or my driveway to see if my car is there, I am probably going to have no idea who used it. If we add in that I generally leave the garage door open, the car unlocked and sometimes leave the keys in the ignition as well...
Well.
That is pretty much the parable that most closely matches investigating copyright theft from, "an individual downloader" stand point. Now one who is actively disseminating copyrighted works is a bit easier to track down and considering the much greater scope of damages I think it behooves society to attempt to investigate a bit more closely and possibly a bit more surrendering of freedom with such an investigation (such as possibly having to turn over computer equipment for forensic investigation if there is a surfit of evidence against the person and so forth).