I just made a wedding cake, sometimes this happens and sometime it doesn't. But when I iced my cake it was very smooth then after it dries and sets it looks sorta rough . Not really cracks but no longer as smooth as before. It also seems when I move them it looks like they get worse. Like I said before when I have finished icing it is smooth as can be.
I don't really know about it looked rough, but I know that if you don't have your cake on a sturdy enough base, it can flex, making the cake shift and that will cause cracks and roughness. Wish I new why it did it on its own...sorry! Maybe its the recipe use??