Great discussion.  I would also like to point out that if a computer is mining, esp ordinary machines, this will tie up all processes and make the machine very slow.  I'm sure most owners will notice and do something about it, i.e. reformat

You are correct.  Click fraud and stealing credit card information would be more profitable... with that being said, mining for bitcoins is more legit at this point.

It's a tug-a-war game.  Haa....