Check out the photograph above. This was taken while traveling in a car. Of particular focus are the lines on the road - they are actually straight, but show up as curved in the photograph.
When cameras were first added to cell phones, they were small, slow and blurry. The sensors were tiny, the lenses were basically plastic and the processors were slow. While the megapixel count has gone up, the optics have gotten better, the biggest bottleneck still remains the processing speed.
At least the Android platform has taken an interesting approach to overcoming this processing speed bottleneck. It seems the sensor is read in sequence, line by line, starting from the top. The advantage with the approach is obvious - the camera can process one line at a time, keeping the picture sharp and well processed.
The side effect is the effect showing up in the picture above. The straight lines on the road, show up as curved because the car moved in the time between when the first line of the sensor was read and the last.