To combat linkjacking, people with editor auth can replace linkjacked urls with the url of the original source. The original submitter still gets the karma points though; he was after all the one who brought it to everyone's attention.

I'm not sure I understand the motive behind the linkjacking. If ze is after a higher pagerank then ze should have noticed that YCnews uses rel=nofollow. If its karma then ze should have spotted that there is only karma gains when its a direct link. If its click throughs on the referal links then I'm pretty sure that the kind of people who read YCnews already have a paypal account and dont want to join payperpost.

Am I missing something?