Yeah I get that alot too, I have no reason to assume it is not to do with the current events of beta update and what not. I am sure that when everything is back to normal with mods ect. It wont happen.
Not sure if it works on those large ones, but when one appeared in my own house, I restarted minecraft and it seemed to be fixed for a time.
So I was walking along, and there was this chunk missing. Along with the chunk was a section that had not loaded the grass, so i was able to see this interesting mine section.. 0.o looks like someone's base! Any takers? This is on the PVP server
The part where you can see the underground but still jump on the un-rendered grass ect. has been there a while. Often you get it after travelling a bit from warping or just from warping, to fix this you can just warp there again and it will re-render correctly. These don' annoy me as much but the chunks I could do without