Can ISPs be trusted?

[gilpel at altern.org]

Most people trust their ISP, and rightly so, I suppose. But what if an ISP
was a vilain? :) What kind of access would it have to its users'
computers? Isn't it the same as a client connected to a server? The server
being root, it has full access to the client.

Of course, the ISP doesn't have the password of the client's computer, but
it transmits data back and forth to its users' computers all day long.

If suppose this is a rather basic networking question, but given my
knowledge on the matter, I have a hard time figuring this out.