There's varying options for this. I suppose there should be the potential for HHP damage if your player is in the effected area, as well as the 'filling in' of certain squares. At the moment however this might be more of a positive than a negative for nearly mined out spots, because all squares count as 'ore'. I don't know if this is intended to be a lasting feature... but if it were changed so that default squares are not valuable, then filling in squares would be a negative you want to protect against.
I suggested cave-ins to jorb before in-game and he said they had already considered it together with support beams. It might make it in or it might not.
The ones who see things differently.
You can praise them, disagree with them, quote them, disbelieve them, glorify or vilify them. About the only thing you can't do is ignore them. And while some may see them as the crazy ones, we see genius.