Well, I am an electrical engineer.

No, electricity can't be slowed down. Technically it travels at a group velocity that's close to the speed of light.

Now many of the other answers are likely: 1) the outlet is switched off when you turn off a switch somewhere or requires a keycard when in the room. Some even use motion detectors. I've had laptops go to sleep and deplete when I though they were charging. 2) Unlikely that the socket is on a dimmer - most dimmers do bad things to switching power supplies and even linear ones don't like it as they modifiy the shape of the sine wave power. 3) Brown outs are unlikely also, you would notice this in the room and it would be big news. Brownouts can cause major havoc with equipment - so much so that power companies perfer to use rolling blackouts in most places I'm familiar with.

So, really nothing Marriott - or any other hotel would or could do to slow down the charging rate on your charger. Something is different - for sure - but it's not the electricity. If current was being limited (typically with a fuse or circuit breaker) it would simply go off. These items, like others have said, consume very small amounts of power.

What is true is that not every power supply is equal. If you plug an Ipad into some USB ports, the ports can't supply enough power to both charge the Ipad and run the Ipad. The Ipad has a way to detect this - it's in the USB standard) - and the Ipad itself does not recharge unless it's turned off. Other devices can do the same. If you use an Ipad charger with an Ipad though - it should charge and run at the same time.

I realize you said it's the same equipment - but something is different if it won't change there and only there.

Billy