If hacking is defined as breaking into a computer system to which you do not have access I definetly think hacking should be punishable. Wether to send people to jail or not should depend on the circumstances.

Often access is restricted due to the nature of the data. If the data is sensitive I think the hacker shouldn do some time. If information is edited or stolen the hacker should *always* go to jail.

So in general, hackers should always be punished for their trespassing and sent to jail if they fiddle around while trespassing.

I think it is naive to say that you should thank hackers that let you know of their weaknesses.
It's like saying that you should thank people that wake you up in the middle of the night, in your own bedrom, for pointing out that your locks can easily be picked.

But that is just my two cents