This is a myth. If you didn't commit a crime, you aren't on the hook for it.This is a nice theory. In Germany, if you are the owner of a SIM card associated with a crime, it is well possible that a prosecutor will consider this sufficient for a warrant, and the police will visit you early in the morning, taking away all your digital devices for something between three months and some years.
Regarding the Wi-Fi hotspot examples you provided (which are not quite the same), in Germany there is a nice legal construct called the "Störerhaftung" (liability for interference), in which you have a civil liability for e.g. copyright violation commited over your uplink.
(IANAL)