Marcus, this is what the USGA suggests as possibly being serious enough to warrant a DQ...
A.In deciding whether a player has committed a serious breach of Rule 1-2, the Committee should consider all aspects of the incident. Given the different impact on players in match play and stroke play, it is possible for the same act to constitute a serious breach of Rule 1-2 in stroke play but not in match play. In many cases in match play (e.g., a player who intentionally stops his ball from entering a water hazard), a penalty of loss of hole is sufficient while in stroke play the player should be disqualified for a serious breach. In some cases (e.g., the purposeful act of damaging the line of putt referred to in Decision 1-2/1), a penalty of disqualification in match play may be appropriate.