I cant remember october but I mine a lot to build a huge castle and by the protection stonea.  I stay away from any areas that looked built up but I do break in to areas when I mine that have been mined before but if I see anything that looks taken or modified I take another route around places. I have entered a room once a while ago that had been constructed with a few water features in it but I put the blocks back and tunnelled around the area.  If I did anything back then then it was not intentional.  Highly enchanted spades and axes can blast away huge areas fast though.  I do tend to mine on square up from bedrock to avoid most people's areas though.