Random blinks on lcd when moving extruder by hand

Hi everyone, 

I just noticed a strange thing, when my printer is off and I move the extruder by hand I'm getting a random short blinks on the lcd, words or single pixels. What do You thing about it?

Thanks! ;)

"Any electric motor will also output a voltage when it’s freely spinning. Stepper motors are much better at this because they have many times more poles to pass next to each other thus generating electrical pulses."

http://hackaweek.com/hacks/?p=595

So You think that it is a normal behavior? 

I consider this inadequate electrical design, but it’s normal behavior of the M200.

You can also create electro magnetic charges by scratching the bed with the spatula that influences the controller.

Ok. Thank You for help :)