I know one of my window units on my house does that. It's supposed to. Instead of letting the condensation drain out, they make it evaporate, which in theory improves the heat transfer out of the condenser. So the air it pulls in to blow out through the condenser makes the condensation evaporate, cooling the air, so it can pickup more heat as it passes through the condenser.
On really humid days, the evaporation can get really behind, and I believe that's when you hear the fan hitting the water. Either that, or they are using the fan to "pump" the water up so it can evaporate better.
Of course, I could also be completely wrong.