This iPhone 3G tried to compete against some water...
...and lost badly. A teardown of it in the first pic:
See the little orange numbers on the connectors? They indicate the parts´assembly sequence - kinda nice feature from Apple...sadly they stopped doing this in their later iPhone models.
Now look at the battery...it bloated and became about three times as thick as normal. As space in the cell-phone is rather limited...
...its high pressure flexed the main logic board (it is indeed permanently curved now ;-). Please also note the severe corrosion on the SMD circuitry - especially on the left side in the next photo: