It keeps more than the RAM going. Maybe depends on the sleep state. I can charge my phone from my computer while it's sleeping, and of course wake it up from the mouse/keyboard. And I think there are even sleep states that keep the fans going. I'm sure I've had to change something on one of my computers to stop the fans when it sleeps.

Nonplussed jackals.

Power downs due to exhausting the battery WILL kill the HDD. I have a dead Asus here to prove it. The distaff side, despite warnings to the contrary*, was in the habit of hitting the power button instead of doing a proper shutdown. How this could have even occurred (see *) could be discussed at length for the better part of a fortnight or nine.