Actually, that wad a babble has a grain of truth. A larger object has more Surface Area with which to hold itself up on. Granted, a rock still won't float unless it's very light and very spread out, but the general process is still the same.
Denser objects (rocks) will sink into less dense ones (like water). However, the continents to float in a manner, as they float on the denser rock beneath them. Ocean floor rock is denser then continental rock, thus it sinks to the bottom. It is still less dense then the molten rock in the mantel, so it floats on that. So, in a weird kind of way, LBF is right. The crust floats on the mantle like ice on a pond.
Surface area matters when there is an attractive force between the molecules in the liquid. Such as the hydrostatic force on water. The orientation of the object then matters, it's how bugs and messiahs can walk on water. Once the orientation changes the object will sink. Are you suggesting that the orientation of your supposed "floating" rocks has never changed? Are you an earthquake denier?
I have experienced an earthquake. I even had a dream about one last night.