When boats are destroyed by lava and by hitting a wall simultaneously, a boat, 2 sticks and 3 planks drop.

VIDEO (not by me): http://www.youtube.com/watch?v=eoqK47XMKHw

I think this is caused by the game receiving a "boat hit lava" event as well as a "boat hit block at speed" event, causing it to drop the things from both drops. Unfortunately, as this drops another boat, it is possible to infinitely generate sticks and planks.