Take a laptop left on the train isn't a very good analogy. The train is essentially a public space (for anyone holding a ticket, at least) and people have a right to be there.
Getting in to PIN-less voicemail boxes is like walking down a street and checking which doors are unlocked, and then assuming a lack of security means the owner is permitting you to take whatever you can find inside.
Getting in to PIN-less voicemail boxes is like walking down a street and checking which doors are unlocked, and then assuming a lack of security means the owner is permitting you to take whatever you can find inside.