Shutter Question

[jaayres20]

I have been thinking a lot about shutters lately and I know I should know the answer to this question but why is a shutter even necessesary?  Obviously it is necessary for film but why for digital?  Why can't the power to the sensor power on and off according to the "shutter speed"?  Why isn't that possible?

[ChrisAnderson]

From http://www.steves-digicams.com/knowledge-center/why-digital-cameras-have-mechanical-shutters.html#b :
The  mechanical shutter controls the amount of charge accumulated on the sensor, and this simple mechanical device can be used to simplify the circuitry on the sensor itself thereby generally improving image quality and reducing noise.

[distant.star]

.
It's all about the megatronic receptors.

If they could engineer the positive luminators to activate on first current, the pinocchio pixelators could bypass the bayer filter. Then the RGB filter arrays would work directly off the incoming photons.

One of these days perhaps! I know those Canon engineers are all over this one.

Obviously, I have no idea. My unknowledgeable guess would have to do with speed of powering up the sensor.