Some things about block breaking

When smooth stone is broken, you get cobble -

Smooth stone -> cobble

So, let's take this into account. The game has one block given as a result of damaging a placed one. So....

Stone bricks -> cracked stone bricks

Sandstone -> sand (4)

Breaking things to yield more things will provide more of that delicious popping noise, but could get annoying:

diamond block -> diamond (9)

iron block -> iron (9)

gold block -> gold (9)

you get the picture. If this were to happen there'd certainly be a lot more multiple item drops per block break (don't lie, you like it when that happens - even if you lose those planks from your bookshelf). It'd add another level of realism, but i'd like to counter it by making silk touch a lot more common.