Neat little video:
[fixed embedding - thanks]
No modern video camera has a physical / mechanical shutter - it's all achieved by switching of photosites etc. The physical layout is that the CCD construction allows for 'buffer' sites alongside the photo sites. Logically speaking, the chip is activated, then switched off, and the results buffered, then the read/conversion process to get the data off the chip takes place.
Now, I oversimplified the rolling shutter a bit in my earlier post - I'm obviously not going to get away with that.. so:
The actual CMOS capture process is: row is reset, row is 'activated', <pause to capture>, row deactivated, row read off. My understanding is that each process 'scans' down the chip. So, if you have a slow shutter speed, the 'activate' scan will have reached the bottom before the 'deactivate/read' scan starts at the top. If the shutter speed is fast the activate scan is 'chased' down the chip by the deactivate, the collection phase is shorter than the scan, so the scan part is very significant wrt to the overall exposure.
In the first case, skew/wobble will be minimised, in the second maximised. However, the issue is also significantly affected by the speed at which the scan progresses. That is down to the sheer amount of data to be read (more megapixels=bad), and the rate at which the scan can proceed (basically quality of the circuitry).
Given the basics of exposure, I see no reason why a bullet cam would be running a faster shutter speed than a 'proper' camera, in fact quite the opposite (but I will admit that is an opinion on my part, if a somewhat educated one). Also in my opinion, the likely reason why cheap bullet cams skew badly is because they aren't running expensive to make, highly optimised sensor chips, the 'scan' process is slower, skew is greater..
To which: Why CMOS? CCD chips require a lot of ancilliary circuitry and power to drive them, and process the signals. CMOS chips allow you to build it all on one die, integrate the processing, and require less power. Economy, plain and simple..