Security in Internet Connection provided by the various company.

Hi,
I know several people who use others' unsecured connections in their neighborhoods to connect to the internet, for example, at a local library, restaurant or using a neighbor's connection.
Can the people or company who are actually paying for the connection have any access to the others' information, such as being able to read e-mails, see passwords, financial transactions, IMs, view or hear Skype conversations, etc.?
I was discussing this with a neighbor, who said "If they don't know enough to secure their connection with a password, they probably wouldn't know anything about seeing who else is using their connection or what they are doing on it."
But what do you think?
