But isn't it enough to use it just for metadata and not the pyload itself? (provided that's possible)
That's because a copyright holder could easily host a copy of some pirate film on your new network, and then just see the destination of the data packets.
AFAIK, cops can't deal you actual drugs and then arrest you for it.
Sometimes its legal, depends where you are and how it was done.
> An expert witness affidavit stated that IP addresses linked to Prenda's Minnesota and Florida offices and John Steele, had themselves been identified in 2013 as the initial "seeders" (sharers) of some pornographic media, tagged for "fast" sharing on file-sharing networks, which would be followed up by threat of legal action
Why not? This sounds like a misunderstanding of entrapment
"Entrapment" is actually quite narrow. IANAL, but my understanding is it requires showing that you wouldn't have done the illegal activity without the involvement of the police.
Harassing a person for months to buy weed qualifies; posing as a drug dealer and offering drugs to the people who pass by you, does not.