Dave Letterman teed off on Jay Leno earlier this week in relation to the NBC 'Tonight' mess, and now Leno is fighting back directly at his nemesis -- only this time, it's personal instead of business. While Letterman generally kept his Leno insults showbiz-related, Leno fired off a marriage joke on Wednesday night that will surely hit close to home -- literally -- for Letterman, who last year admitted to having extramarital affairs. Did Jay go too far? What He Said After the Jump!