Im pretty sure everyone already knows of this. It can also screw your monitor up for good.
I did it at my job with some computers and my managers thought it was funny but if I did it to the register with the magnet that takes the security devices off i would be fired....so i didnt.
My buddy accidently did that to our TV. My dad woke me up the next morning pissed as hell ripping the covers off of me going WHAT THE HELL DID YOU DO TO THE TV!