This is a no-brainer.  What's hard to fathom is that people are even debating whether the Masters should have disqualified Tiger Woods for an illegal drop or for signing an incorrect scorecard.  On the 15th hole Friday,  Tiger hit a beautiful approach shot that unfortunately (for him) bounced off the flagstick and directly into a nearby pond.  Here's what happened next , according to Woods (per the New York Times):

“I went down to the drop area, that wasn't going to be a good spot, because obviously it's into the grain, it's really grainy there.  . . And it was a little bit wet so it was muddy and not a good spot to drop. So I went back to where I played it from, but I went two yards further back and I took, tried to take two yards off the shot of what I felt I hit.” (Emphasis supplied.)

Note Woods' words closely, "I went two yards further back and . . . tried to take two yards off the shot . . . I hit."  The effective USGA rule 26 (a) provides that when a player decides to take an unplayable lie he must drop his ball “as near as possible” to where he had hit his last shot.  Tiger clearly violated the rule when he dropped the ball two yards from where he had hit his last shot.  In so doing, he received an enormous advantage over every other player in the field.  He was able to go to school on himself by adding two yards to the actual distance he had to hit recognizing that he had hit the last shot a little too hard.  He also avoided his divot.

The Masters Competition Committee elected not to disqualify Tiger for signing an incorrect scorecard, i.e., without the 2-stroke penalty.  Instead, it assessed the penalty which Tiger should have given himself.  They based this decision on a recent codicil to Rule 33 that previously mandated disqualification under these circumstances. 

The codcil found at Rule 33-7/4.5 addresses a situation where a player is not aware he has breached a Rule because of facts that he did not know and could not reasonably have discovered prior to returning his score card. Under this revised decision and at the discretion of the Committee, the player still receives the penalty associated with the breach of the underlying Rule, but is not disqualified.''  USGA Comment to Rule 33-7/4.5.

But, Tiger had to know of all the circumstances before he signed his scorecard.  He knew the spot where he hit the ball that went into the drink and he knew that he didn't drop the ball there.  He didn't penalize himself.  He tried to advantage himself at the expense of every other competitor.  The rules mandate disqualification.