When we first moved into our house we discovered that water was leaking through a door in my office on the second floor, running along a joist and then dropping through the ceiling in our family room.  We had a nice bubbling effect before the paint and drywall started falling onto our coffee table.  The picture to the left is from an apartment in Russia that has some kind of magical, water-holding material that caught all the water leaking from an apartment above and created what I’d call some significant bubbles in the ceiling.  If our ceiling had done that I’d have been tempted to repair the leak but keep the ceiling and paint a bra on it.