It was possibly caused by a small thermalnuclear devise

the word would be hydrostatic pressure.
what occurs is several different things.
1. to much setting materials used to stick the wall tile can cause this
2. or tile were set to close together and tempature change can cause this
3. on floor tiles (this happened in my house)
I tiled the entire house 5 years ago. The hurricanes caused my home to flood and the water was forced in the house by high winds and moisture got in between the concrete slab and the setting materials and caused hdro static pressure. Now my floor sounds like I have a lot of hollow tiles. Thank GOD for insurance.
The wall tiles that popped off, was the mastic left on the walls or left on the tiles or both. any and all tile have to have a minimum of 1/16th of a grout joint even marble that has butt joint. Does this help?
Could it of just been the tiles werent properly set. sometimes if the tile was stuck om top of dry wall mud the water from the glue will activate the mud and loosen the tiles. big no no

When the tile came off about half the cement was left on the wall. Not really in patches - the cement seems to have cracked leaving a uniform layer on both wall and tile. The wall and back of the tile seemed to be dry even though the bathroom isn't exactly well ventilated.  The wall showed no sign of water damage. It was quite hard to remove the remaining cement from the wall but easier from the tile. I guess it's possible the wrong cement was used.

Otherwise I can only think that it was caused by the tiles being jammed together and expansion. I had to file all the edges a bit to get them back in the space they came out of they were that tight.

They are over the bath so I used waterproof cement to put them back on and will see if any others come away.

Well they do have a pattern that makes you want to take a hammer to the lot Perhaps later.

No but they look like the sort of tiles you could find on a thousand housing estates built 10 years ago.

On another subject...  does everyone here know about the "duck tiles"? or is it just my friends and I that can see the duck?

[quote author=CWatters  link=1137358056/0#5 date=1137492421]When the tile came off about half the cement was left on the wall. Not really in patches - the cement seems to have cracked leaving a uniform layer on both wall and tile. The wall and back of the tile seemed to be dry even though the bathroom isn't exactly well ventilated.  The wall showed no sign of water damage. It was quite hard to remove the remaining cement from the wall but easier from the tile. I guess it's possible the wrong cement was used.

Otherwise I can only think that it was caused by the tiles being jammed together and expansion. I had to file all the edges a bit to get them back in the space they came out of they were that tight.  

They are over the bath so I used waterproof cement to put them back on and will see if any others come away. [/quote] We don't use cement base to stick up wall tiles, we use glue. I think you call it sticky there. Sticky makes it sticky. lol  Cement base we call several things like thin set, mud. If you use mud to stick up wall tiles it will evenuallyl fail on you. It dries out and the vibration will caused to fall off. another very good possibility is the thickness of the cement based material was to thick and should of use a wire lath to keep it from breaking off. wrong materials used in my opinion with looking atg it.