I guess if downvotes didn't use up one's power these graphs would look a little different!
True, but can you imagine the abuse of flags were 'free'?!
One other thing I have noticed is that new users quite often think these comments are legitimate and thank the damn spammers!!
Yes others have mentioned this, and you can't blame the newer users for appreciating even a short comment.
Good point about the down votes.
Something will have to be done though otherwise you wan't be able to see the legitimate comments for all the spam as the site gains more users.
Its a work in progress and recent reports suggest that the battle is slowly being won, although it will remain a war of attricion for a while I think. Cheers!