There are a lot of questions being asked now in the Rules Forum, which implies there has been a change in a core mechanic - which there has. I don't view that as a good thing: if it isn't broken, don't fix it. All this came about because someone asked "what happens if I'm in base-to-base with a bunch of small bases and I trample 0"?" Given that the game has 0.5" melee range on all models, the odds of getting more than 2-3 small based models with this technique was nearly non-existent.
But alas, strange rulings and impending errata are not my providence.