2009-10-01 : All creatures are dealt damage, not just ones controlled by the targeted lands’ controller(s).

2009-10-01 : Casting a Trap by paying its alternative cost doesn’t change its mana cost or converted mana cost. The only difference is the cost you actually pay.

2009-10-01 : Effects that increase or reduce the cost to cast a Trap will apply to whichever cost you chose to pay.

2009-10-01 : If both targeted lands are illegal targets by the time Lavaball Trap resolves, the entire spell doesn’t resolve. No creatures are dealt damage.

2009-10-01 : You may ignore a Trap’s alternative cost condition and simply cast it for its normal mana cost. This is true even if its alternative cost condition has been met.

2009-10-01 : You may target any two lands, not just ones that entered the battlefield this turn.