I found some extremely deep 1x1 holes in wilderness,they are deep enough to kill you.Whats the fun for making these holes?
I would say most of them are people wanting to get down to bedrock as fast as possible so they dig straight down.
Should, but wont. *Shrugs* Just watch your footing at all times and keep a block at hand so you can quickly place one beneath you if you drop. Saved my life a few times doing that.